in a triangle with the side lengths 5, 7, 9 length units, the largest angle x is
A) x>90
B) x=90
C) x<90
We have given the sides of triangle 5,7,9.5,7,9.5,7,9.
Largest angle would be on the opposite of largest side,
We know,
cosA=b2+c2−a22bccosA = \dfrac{b^2+c^2-a^2}{2bc}cosA=2bcb2+c2−a2
cosA=52+72−922×5×7cosA = \dfrac{5^2+7^2-9^2}{2 \times 5 \times 7}cosA=2×5×752+72−92
cosA=−2170cosA = -\dfrac{21}{70}cosA=−7021
A=107.45∘A = 107.45^{\circ}A=107.45∘
Hence the angle will be greater than 90∘90^{\circ}90∘
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