Find the curvature, the radius and the center of curvature at a point.
y=sin x, x = pi/2
"y'=\\cos x, y''=-\\sin x"
"K=\\dfrac{|-\\sin x|}{[1+\\cos ^2 x]^{3\/2}}"
"x=\\pi\/2"
"K=\\dfrac{|-\\sin (\\pi\/2)|}{[1+\\cos ^2 (\\pi\/2)]^{3\/2}}=1"The radius of curvature of a curve at a point is called the inverse of the curvature "K" of the curve at this point:
"x_C=x-\\dfrac{y'(1+(y')^2)}{y''}"
"y_C=y+\\dfrac{1+(y')^2}{y''}"
"x=\\pi\/2"
"y(\\pi\/2)=\\sin(\\pi\/2)=1""y'(\\pi\/2)=-\\cos(\\pi\/2)=0"
"y''(\\pi\/2)=-\\sin(\\pi\/2)=-1"
"x_C=\\pi\/2-\\dfrac{0(1+(0)^2)}{-1}=\\pi\/2"
"y_C=1+\\dfrac{1+(0)^2}{-1}=0"
"C(\\pi\/2, 0)"
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