題目 Problem Evaluate ∬Rcos(y−xy+x) dA\displaystyle\iint_R \cos\left(\frac{y-x}{y+x}\right)\,dA∬Rcos(y+xy−x)dA where RRR is the trapezoidal region with vertices (1,0)(1,0)(1,0), (2,0)(2,0)(2,0), (0,2)(0,2)(0,2) and (0,1)(0,1)(0,1). 解答
