iii) find curvature r(t) = ( Β½ Cost, 1-sint, -3/2 cost)
"r''(t)=\\langle -\\dfrac{1}{2}\\cos t, \\sin t, \\dfrac{3}{2}\\cos t\\rangle"
"r'(t)\\times r''(t)=\\begin{vmatrix}\n i & j & k \\\\\n -(\\sin t)\/2 & -\\cos t & (3\\sin t)\/2\\\\\n-(\\cos t)\/2 & \\sin t & (3\\cos t)\/2\n\\end{vmatrix}"
"-j\\begin{vmatrix}\n -(\\sin t)\/2 & (3\\sin t)\/2 \\\\\n -(\\cos t)\/2 & (3\\cos t)\/2\n\\end{vmatrix}"
"=-\\dfrac{3}{2}i+\\dfrac{3}{4}\\sin t\\cos tj-\\dfrac{1}{2}k"
"=\\dfrac{1}{4}\\sqrt{40+9\\sin^2t\\cos^2t}"
"|r'(t)|=\\sqrt{\\dfrac{1}{4}\\sin^2t+\\cos^2t+\\dfrac{9}{4}\\sin^2t}"
"=\\dfrac{1}{2}\\sqrt{4+6\\sin^2t}"
"k=\\dfrac{|r'(t) \\times r''(t)|}{|r'(t)|^3}=\\dfrac{\\dfrac{1}{4}\\sqrt{40+9\\sin^2t\\cos^2t}}{\\dfrac{1}{8}(4+6\\sin^2t)\\sqrt{4+6\\sin^2t}}"
"=\\dfrac{\\sqrt{40+9\\sin^2t\\cos^2t}}{(2+3\\sin^2t)\\sqrt{4+6\\sin^2t}}"
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