Question

扇形的面积是12.56平方厘米,半径是4厘米,则圆心角是?

Answer 1

1/2×L×R=12.56

1/2×L×4=12.56

2L=12.56

L=6.28

L=nπr/180

6.28=n×π×4/180

n=90

圆心角是90度