∫[0,π/2]d(α)∫[0,cosα]f(rcosα,rsinα)rd(r)
=∫[0,1]dx∫[0,根号(1/4-(x-1/2)^2)]f(x,y)dy
就是把r=cosα-->r^2=rcosα-->x^2+y^2=x
然后画图,就可以看出来了
∫[0,π/2]d(α)∫[0,cosα]f(rcosα,rsinα)rd(r)
=∫[0,1]dx∫[0,根号(1/4-(x-1/2)^2)]f(x,y)dy
就是把r=cosα-->r^2=rcosα-->x^2+y^2=x
然后画图,就可以看出来了