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=∫θ2θ1√θ2+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=∫θ2θ1√r2+(drdθ)2dθ=∫θ2θ1√θ2+1dθ