Tentukan ∂f∂r\frac {\partial f} {\partial r}∂r∂f dan ∂f∂θ\frac {\partial f}{\partial \theta}∂θ∂f dari fungsi-fungsi berikut: a. f(x,y)=3x2−5y2;x=rsin2θ;y=rcosθf(x,y) = 3x^2-5y^2; x=r \sin 2 \theta; y=r \cos \thetaf(x,y)=3x2−5y2;x=rsin2θ;y=rcosθ b. f(x,y)=4x2+7y2;x=sin(r−θ);y=cos(θ−r)f(x,y)= 4x^2+7y^2; x=\sin (r-\theta);y=\cos(\theta-r)f(x,y)=4x2+7y2;x=sin(r−θ);y=cos(θ−r)