(3) Compute for the following: sin(x + y) = yz cos x; cos(x - y) = y sin x; Vay = 1+x y; + = 1; y Vaty = vay = 6; x cosy + cos 2y = cosy. [5 marks] (4) Where is the function h(x) = (x - 1 + x + 2| differentiable? Compute h'(x) whenever it is defined. [5 marks]