( i ) Fourier sine transform of f ( x ) f s ( ω ) = 2 π ∫ − ∞ ∞ f ( x ) sin ( ω x ) d x = 2 π ∫ 0 10 x 2 sin ( ω x ) d x + 2 π ∫ 10 ∞ 0 × sin ( ω x ) d x = 1 ω 2 π ∫ 0 10 x 2 d ( − cos ( ω x ) ) = 2 π ω 2 ( − x 2 cos ( ω x ) ∣ 0 10 + 2 ∫ 0 10 x cos ( ω x ) d x ) = 2 π ω 2 ( − 100 cos ( 100 ω ) + 2 ω ∫ 0 10 x d ( sin ( ω x ) ) ) = 2 π ω 2 ( − 100 cos ( 100 ω ) + 2 ω x sin ( ω x ) ∣ 0 10 − 2 ω ∫ 0 10 sin ( ω x ) d x ) = 2 π ω 2 ( − 100 cos ( 100 ω ) + 2 ω x sin ( ω x ) ∣ 0 10 + 2 ω 2 cos ( ω x ) ∣ 0 10 ) = 2 π ω 2 ( − 100 cos ( 100 ω ) + 20 ω sin ( 20 ω ) + 2 ω 2 ( cos ( 10 ω ) − 1 ) ) Fourier cosine transform of f ( x ) f c ( ω ) = 2 π ∫ − ∞ ∞ f ( x ) cos ( ω x ) d x = 2 π ∫ 0 10 x 2 cos ( ω x ) d x + 2 π ∫ 10 ∞ 0 × cos ( ω x ) d x = 1 ω 2 π ∫ 0 10 x 2 d ( sin ( ω x ) ) = 2 π ω 2 ( x 2 sin ( ω x ) ∣ 0 10 − 2 ∫ 0 10 x sin ( ω x ) d x ) = 2 π ω 2 ( 100 sin ( 100 ω ) + 2 ω ∫ 0 10 x d ( cos ( ω x ) ) ) = 2 π ω 2 ( 100 sin ( 100 ω ) + 2 ω x cos ( ω x ) ∣ 0 10 − 2 ω ∫ 0 10 cos ( ω x ) d x ) = 2 π ω 2 ( 100 sin ( 100 ω ) + 2 ω x cos ( ω x ) ∣ 0 10 − 2 ω 2 sin ( ω x ) ∣ 0 10 ) = 2 π ω 2 ( 100 sin ( 100 ω ) + 20 ω cos ( 20 ω ) − 2 ω 2 sin ( 10 ω ) ) ( i i ) Fourier sine transform of f ( x ) f c ( ω ) = 2 π ∫ − ∞ ∞ f ( x ) cos ( ω x ) d x = 2 π ∫ 0 1 x cos ( ω x ) d x + 2 π ∫ 1 2 ( x + 1 ) cos ( ω x ) d x + 2 π ∫ 2 ∞ 0 × cos ( ω x ) d x = 1 ω 2 π ( ∫ 0 1 x d ( sin ( ω x ) ) + ∫ 1 2 ( x + 1 ) d ( sin ( ω x ) ) ) = 1 ω 2 π ( x sin ( ω x ) ∣ 0 1 − ∫ 0 1 sin ( ω x ) d x + ( x + 1 ) sin ( ω x ) ∣ 1 2 − ∫ 1 2 sin ( ω x ) d x ) = 1 ω 2 π ( sin ( ω ) + cos ( ω x ) ω ∣ 0 1 + 3 sin ( 2 ω ) − 2 sin ( ω ) + cos ( ω x ) ω ∣ 1 2 ) = 1 ω 2 π ( sin ( ω ) + cos ( ω ) ω − 1 ω + 3 sin ( 2 ω ) − 2 sin ( ω ) + cos ( 2 ω ) ω − cos ( ω ) ) = 1 ω 2 π ( − sin ( ω ) + 3 sin ( 2 ω ) + cos ( 2 ω ) ω − 1 ω ) Fourier cosine transform of f ( x ) f c ( ω ) = 2 π ∫ − ∞ ∞ f ( x ) cos ( ω x ) d x = 2 π ∫ 0 1 x cos ( ω x ) d x + 2 π ∫ 1 2 ( x + 1 ) cos ( ω x ) d x + 2 π ∫ 2 ∞ 0 × cos ( ω x ) d x = 1 ω 2 π ( ∫ 0 1 x d ( sin ( ω x ) ) + ∫ 1 2 ( x + 1 ) d ( sin ( ω x ) ) ) = 1 ω 2 π ( x sin ( ω x ) ∣ 0 1 − ∫ 0 1 sin ( ω x ) d x + ∫ ( x + 1 ) sin ( ω x ) ∣ 1 2 − ∫ 1 2 sin ( ω x ) d x ) = 1 ω 2 π ( sin ( ω ) + cos ( ω x ) ∣ 0 1 + 3 sin ( 2 ω ) − 2 sin ( ω ) + cos ( ω x ) ∣ 1 2 ) = 1 ω 2 π ( sin ( ω ) + cos ( ω ) − 1 + 3 sin ( 2 ω ) − 2 sin ( ω ) + cos ( 2 ω ) − cos ( ω ) ) = 1 ω 2 π ( − sin ( ω ) + 3 sin ( 2 ω ) + cos ( 2 ω ) − 1 ) f s ( ω ) = 2 π ∫ − ∞ ∞ f ( x ) sin ( ω x ) d x = 2 π ∫ 0 1 x sin ( ω x ) d x + 2 π ∫ 1 2 ( x + 1 ) sin ( ω x ) d x + 2 π ∫ 2 ∞ 0 × sin ( ω x ) d x = 1 ω 2 π ( ∫ 0 1 x d ( − cos ( ω x ) ) + ∫ 1 2 ( x + 1 ) d ( − cos ( ω x ) ) ) = 1 ω 2 π ( − x cos ( ω x ) ∣ 0 1 + ∫ 0 1 cos ( ω x ) d x − ( x + 1 ) cos ( ω x ) ∣ 1 2 + ∫ 1 2 cos ( ω x ) d x ) = 1 ω 2 π ( − cos ( ω ) + sin ( ω x ) ω ∣ 0 1 − 3 cos ( 2 ω ) + 2 cos ( ω ) + sin ( ω x ) ω ∣ 1 2 ) = 1 ω 2 π ( − cos ( ω ) + sin ( ω ) ω − 3 cos ( 2 ω ) + 2 cos ( ω ) + sin ( 2 ω ) ω − sin ( ω ) ω ) = 1 ω 2 π ( cos ( ω ) − 3 cos ( 2 ω ) + sin ( 2 ω ) ω ) \displaystyle
(i)\\
\textsf{Fourier sine transform of}\,f(x) \\
\begin{aligned}
f_s(\omega) &= \sqrt{\frac{2}{\pi}}\int_{-\infty}^{\infty} f(x) \sin(\omega x) \mathrm{d}x\\
&=\sqrt{\frac{2}{\pi}}\int_0^{10} x^2 \sin(\omega x) \mathrm{d}x + \sqrt{\frac{2}{\pi}}\int_{10}^{\infty} 0 \times \sin(\omega x) \mathrm{d}x\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\int_0^{10} x^2 \mathrm{d}(-\cos(\omega x))\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(-x^2 \cos(\omega x)\vert_0^{10} + 2\int_0^{10} x\cos(\omega x) \mathrm{d}x\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(-100 \cos(100\omega) + \frac{2}{\omega}\int_0^{10} x\mathrm{d}(\sin(\omega x))\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(-100 \cos(100 \omega) + \frac{2}{\omega} x\sin(\omega x)\vert_0^{10} - \frac{2}{\omega}\int_0^{10} \sin(\omega x) \mathrm{d}x\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(-100 \cos(100 \omega) + \frac{2}{\omega}x\sin(\omega x)\vert_0^{10} + \frac{2}{\omega^2}\cos(\omega x)\vert_0^{10}\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(-100 \cos(100 \omega) + \frac{20}{\omega}\sin(20\omega) + \frac{2}{\omega^2}(\cos(10 \omega) - 1)\right)
\end{aligned} \\
\textsf{Fourier cosine transform of}\,f(x)\\
\begin{aligned}
f_c(\omega) &= \sqrt{\frac{2}{\pi}}\int_{-\infty}^{\infty} f(x) \cos(\omega x) \mathrm{d}x\\
&=\sqrt{\frac{2}{\pi}}\int_0^{10} x^2 \cos(\omega x) \mathrm{d}x + \sqrt{\frac{2}{\pi}}\int_{10}^{\infty} 0 \times \cos(\omega x) \mathrm{d}x\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\int_0^{10} x^2 \mathrm{d}(\sin(\omega x))\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(x^2 \sin(\omega x)\vert_0^{10} - 2\int_0^{10} x\sin(\omega x) \mathrm{d}x\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(100 \sin(100\omega) + \frac{2}{\omega}\int_0^{10} x\mathrm{d}(\cos(\omega x))\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(100 \sin(100 \omega) +\frac{2}{\omega} x\cos(\omega x)\vert_0^{10} - \frac{2}{\omega}\int_0^{10} \cos(\omega x) \mathrm{d}x\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(100 \sin(100 \omega) +\frac{2}{\omega}x\cos(\omega x)\vert_0^{10} - \frac{2}{\omega^2}\sin(\omega x)\vert_0^{10}\right)\\
&= \sqrt{\frac{2}{\pi \omega^2}}\left(100 \sin(100 \omega) + \frac{20}{\omega}\cos(20\omega) - \frac{2}{\omega^2}\sin(10 \omega)\right)
\end{aligned} \\
(ii)\\
\textsf{Fourier sine transform of}\,f(x) \\
\begin{aligned}
f_c(\omega) &= \sqrt{\frac{2}{\pi}}\int_{-\infty}^{\infty} f(x) \cos(\omega x) \mathrm{d}x\\
&=\sqrt{\frac{2}{\pi}}\int_0^{1} x\cos(\omega x) \mathrm{d}x + \sqrt{\frac{2}{\pi}}\int_1^{2} (x + 1)\cos(\omega x) \mathrm{d}x \\&+ \sqrt{\frac{2}{\pi}}\int_{2}^{\infty} 0 \times \cos(\omega x) \mathrm{d}x \\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\int_0^{1} x\mathrm{d}(\sin(\omega x)) + \int_1^{2} (x + 1)\mathrm{d}(\sin(\omega x))\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(x\sin(\omega x)\vert_0^{1} - \int_0^{1} \sin(\omega x) \mathrm{d}x + (x + 1)\sin(\omega x)\vert_1^{2}\right.\\&\left. - \int_1^{2} \sin(\omega x) \mathrm{d}x\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\sin(\omega) + \frac{\cos(\omega x)}{\omega}\vert_0^{1} +3\sin(2\omega) \right.\\&\left.- 2\sin(\omega) + \frac{\cos(\omega x)}{\omega}\vert_1^{2}\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\sin(\omega) + \frac{\cos(\omega)}{\omega} - \frac{1}{\omega} + 3\sin(2\omega) \right.\\&\left.- 2\sin(\omega) + \frac{\cos(2\omega)}{\omega} - \cos(\omega)\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(-\sin(\omega) + 3\sin(2\omega) + \frac{\cos(2\omega)}{\omega} - \frac{1}{\omega}\right)
\end{aligned} \\
\textsf{Fourier cosine transform of}\,f(x) \\
\begin{aligned}
f_c(\omega) &= \sqrt{\frac{2}{\pi}}\int_{-\infty}^{\infty} f(x) \cos(\omega x) \mathrm{d}x
\\&=\sqrt{\frac{2}{\pi}}\int_0^{1} x\cos(\omega x) \mathrm{d}x + \sqrt{\frac{2}{\pi}}\int_1^{2} (x + 1)\cos(\omega x) \mathrm{d}x \\&+ \sqrt{\frac{2}{\pi}}\int_{2}^{\infty} 0 \times \cos(\omega x) \mathrm{d}x \\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\int_0^{1} x\mathrm{d}(\sin(\omega x)) + \int_1^{2} (x + 1)\mathrm{d}(\sin(\omega x))\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(x\sin(\omega x)\vert_0^{1} - \int_0^{1} \sin(\omega x) \mathrm{d}x + \int (x + 1)\sin(\omega x)\vert_1^{2} \right.\\&\left.- \int_1^{2} \sin(\omega x) \mathrm{d}x\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\sin(\omega) + \cos(\omega x)\vert_0^{1} +3\sin(2\omega) \right.\\&\left.- 2\sin(\omega) + \cos(\omega x)\vert_1^{2}\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\sin(\omega) + \cos(\omega) - 1 + 3\sin(2\omega) \right.\\&\left.- 2\sin(\omega) + \cos(2\omega) - \cos(\omega)\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(-\sin(\omega) + 3\sin(2\omega) + \cos(2\omega) - 1\right)
\end{aligned} \\
\begin{aligned}
f_s(\omega) &= \sqrt{\frac{2}{\pi}}\int_{-\infty}^{\infty} f(x) \sin(\omega x) \mathrm{d}x\\
&=\sqrt{\frac{2}{\pi}}\int_0^{1} x\sin(\omega x) \mathrm{d}x + \sqrt{\frac{2}{\pi}}\int_1^{2} (x + 1)\sin(\omega x) \mathrm{d}x \\&+ \sqrt{\frac{2}{\pi}}\int_{2}^{\infty} 0 \times \sin(\omega x) \mathrm{d}x \\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\int_0^{1} x\mathrm{d}(-\cos(\omega x)) + \int_1^{2} (x + 1)\mathrm{d}(-\cos(\omega x))\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(-x\cos(\omega x)\vert_0^{1} + \int_0^{1} \cos(\omega x) \mathrm{d}x - (x + 1)\cos(\omega x)\vert_1^{2} \right.\\&\left.+ \int_1^{2} \cos(\omega x) \mathrm{d}x\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(-\cos(\omega) + \frac{\sin(\omega x)}{\omega}\vert_0^{1} - 3\cos(2\omega) \right.\\&\left.+2\cos(\omega) + \frac{\sin(\omega x)}{\omega}\vert_1^{2}\right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(-\cos(\omega) + \frac{\sin(\omega)}{\omega} - 3\cos(2\omega) + 2\cos(\omega) \right.\\&\left.+ \frac{\sin(2\omega)}{\omega} - \frac{\sin(\omega)}{\omega} \right)\\
&= \frac{1}{\omega}\sqrt{\frac{2}{\pi}}\left(\cos(\omega) - 3\cos(2\omega) + \frac{\sin(2\omega)}{\omega}\right)
\end{aligned} ( i ) Fourier sine transform of f ( x ) f s ( ω ) = π 2 ∫ − ∞ ∞ f ( x ) sin ( ω x ) d x = π 2 ∫ 0 10 x 2 sin ( ω x ) d x + π 2 ∫ 10 ∞ 0 × sin ( ω x ) d x = ω 1 π 2 ∫ 0 10 x 2 d ( − cos ( ω x )) = π ω 2 2 ( − x 2 cos ( ω x ) ∣ 0 10 + 2 ∫ 0 10 x cos ( ω x ) d x ) = π ω 2 2 ( − 100 cos ( 100 ω ) + ω 2 ∫ 0 10 x d ( sin ( ω x )) ) = π ω 2 2 ( − 100 cos ( 100 ω ) + ω 2 x sin ( ω x ) ∣ 0 10 − ω 2 ∫ 0 10 sin ( ω x ) d x ) = π ω 2 2 ( − 100 cos ( 100 ω ) + ω 2 x sin ( ω x ) ∣ 0 10 + ω 2 2 cos ( ω x ) ∣ 0 10 ) = π ω 2 2 ( − 100 cos ( 100 ω ) + ω 20 sin ( 20 ω ) + ω 2 2 ( cos ( 10 ω ) − 1 ) ) Fourier cosine transform of f ( x ) f c ( ω ) = π 2 ∫ − ∞ ∞ f ( x ) cos ( ω x ) d x = π 2 ∫ 0 10 x 2 cos ( ω x ) d x + π 2 ∫ 10 ∞ 0 × cos ( ω x ) d x = ω 1 π 2 ∫ 0 10 x 2 d ( sin ( ω x )) = π ω 2 2 ( x 2 sin ( ω x ) ∣ 0 10 − 2 ∫ 0 10 x sin ( ω x ) d x ) = π ω 2 2 ( 100 sin ( 100 ω ) + ω 2 ∫ 0 10 x d ( cos ( ω x )) ) = π ω 2 2 ( 100 sin ( 100 ω ) + ω 2 x cos ( ω x ) ∣ 0 10 − ω 2 ∫ 0 10 cos ( ω x ) d x ) = π ω 2 2 ( 100 sin ( 100 ω ) + ω 2 x cos ( ω x ) ∣ 0 10 − ω 2 2 sin ( ω x ) ∣ 0 10 ) = π ω 2 2 ( 100 sin ( 100 ω ) + ω 20 cos ( 20 ω ) − ω 2 2 sin ( 10 ω ) ) ( ii ) Fourier sine transform of f ( x ) f c ( ω ) = π 2 ∫ − ∞ ∞ f ( x ) cos ( ω x ) d x = π 2 ∫ 0 1 x cos ( ω x ) d x + π 2 ∫ 1 2 ( x + 1 ) cos ( ω x ) d x + π 2 ∫ 2 ∞ 0 × cos ( ω x ) d x = ω 1 π 2 ( ∫ 0 1 x d ( sin ( ω x )) + ∫ 1 2 ( x + 1 ) d ( sin ( ω x )) ) = ω 1 π 2 ( x sin ( ω x ) ∣ 0 1 − ∫ 0 1 sin ( ω x ) d x + ( x + 1 ) sin ( ω x ) ∣ 1 2 − ∫ 1 2 sin ( ω x ) d x ) = ω 1 π 2 ( sin ( ω ) + ω cos ( ω x ) ∣ 0 1 + 3 sin ( 2 ω ) − 2 sin ( ω ) + ω cos ( ω x ) ∣ 1 2 ) = ω 1 π 2 ( sin ( ω ) + ω cos ( ω ) − ω 1 + 3 sin ( 2 ω ) − 2 sin ( ω ) + ω cos ( 2 ω ) − cos ( ω ) ) = ω 1 π 2 ( − sin ( ω ) + 3 sin ( 2 ω ) + ω cos ( 2 ω ) − ω 1 ) Fourier cosine transform of f ( x ) f c ( ω ) = π 2 ∫ − ∞ ∞ f ( x ) cos ( ω x ) d x = π 2 ∫ 0 1 x cos ( ω x ) d x + π 2 ∫ 1 2 ( x + 1 ) cos ( ω x ) d x + π 2 ∫ 2 ∞ 0 × cos ( ω x ) d x = ω 1 π 2 ( ∫ 0 1 x d ( sin ( ω x )) + ∫ 1 2 ( x + 1 ) d ( sin ( ω x )) ) = ω 1 π 2 ( x sin ( ω x ) ∣ 0 1 − ∫ 0 1 sin ( ω x ) d x + ∫ ( x + 1 ) sin ( ω x ) ∣ 1 2 − ∫ 1 2 sin ( ω x ) d x ) = ω 1 π 2 ( sin ( ω ) + cos ( ω x ) ∣ 0 1 + 3 sin ( 2 ω ) − 2 sin ( ω ) + cos ( ω x ) ∣ 1 2 ) = ω 1 π 2 ( sin ( ω ) + cos ( ω ) − 1 + 3 sin ( 2 ω ) − 2 sin ( ω ) + cos ( 2 ω ) − cos ( ω ) ) = ω 1 π 2 ( − sin ( ω ) + 3 sin ( 2 ω ) + cos ( 2 ω ) − 1 ) f s ( ω ) = π 2 ∫ − ∞ ∞ f ( x ) sin ( ω x ) d x = π 2 ∫ 0 1 x sin ( ω x ) d x + π 2 ∫ 1 2 ( x + 1 ) sin ( ω x ) d x + π 2 ∫ 2 ∞ 0 × sin ( ω x ) d x = ω 1 π 2 ( ∫ 0 1 x d ( − cos ( ω x )) + ∫ 1 2 ( x + 1 ) d ( − cos ( ω x )) ) = ω 1 π 2 ( − x cos ( ω x ) ∣ 0 1 + ∫ 0 1 cos ( ω x ) d x − ( x + 1 ) cos ( ω x ) ∣ 1 2 + ∫ 1 2 cos ( ω x ) d x ) = ω 1 π 2 ( − cos ( ω ) + ω sin ( ω x ) ∣ 0 1 − 3 cos ( 2 ω ) + 2 cos ( ω ) + ω sin ( ω x ) ∣ 1 2 ) = ω 1 π 2 ( − cos ( ω ) + ω sin ( ω ) − 3 cos ( 2 ω ) + 2 cos ( ω ) + ω sin ( 2 ω ) − ω sin ( ω ) ) = ω 1 π 2 ( cos ( ω ) − 3 cos ( 2 ω ) + ω sin ( 2 ω ) )
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