Question

定积分求椭圆面积,我的思路如下,可答案是错误的,

Answer 1

x^2/a^2+y^2/b^2 =1

x= acosθ

y= bsinθ

dA = (1/2)r^2dθ

= (1/2)[(acosθ)^2 +(bsinθ)^2] dθ