Question

(1)x=3cosθ y=3sinθ 0≤θ≤π/2 (2)x=2cost y=2sint π≤t≤2π

Answer 1

(1)x=3cosθ y=3sinθ 0≤θ≤π/2

(x/3)^2+(y/3)^2=(cosθ)^2+(sinθ)^2=1

x^2+y^2=9,x、y∈[0,1]

为圆心在原点、半径为3的圆在x>=0且y>=0的部分

(2)x=2cost y=2sint π≤t≤2π

同理,x^2+y^2=4,为圆心在原点、半径为2的圆在y