1/2x 2x dx 12) dx X 13) [xe dx 14) [cos -1 x dx 5) [ (In x) dx 15) x 16) (xcos.x d dx 17) sin ln x dx sin in x d 18) cosx+1 cos x edx For each problem, approximate the area under the curve over the given interval using 4 left endpoint rectangles. 19) y=x+3; [-7, -3] -2- 20) y= +x+5; [0,4] 2