r2r\frac{\frac{r}{2}}{r}r2r Sin θ\thetaθ = 12\frac{1}{2}21
θ\thetaθ = sin−1^{-1}−1 (12\frac{1}{2}21) = 30∘^{\circ}∘ = 60∘^{\circ}∘
Length of arc (minor)
ST = θ360\frac{\theta}{360}360θ x 2πr\pi rπr
60360×2π×r=π3\frac{60}{360} \times 2 \pi \times r = \frac{\pi}{3}36060×2π×r=3π
