How do you find the length of the polar curve r=thetar=θ ?

1 Answer
Sep 7, 2014

If thetaθ goes from theta_1θ1 to theta_2θ2, then the arc length of can be found by
L=int_{theta_1}^{theta_2}sqrt{theta^2+1}d thetaL=θ2θ1θ2+1dθ.

Since r=thetar=θ, which gives {dr}/{d theta}=1drdθ=1, we have
L=int_{theta_1}^{theta_2}sqrt{r^2+({dr}/{d theta})^2}d theta =int_{theta_1}^{theta_2}sqrt{theta^2+1}d thetaL=θ2θ1r2+(drdθ)2dθ=θ2θ1θ2+1dθ