If trapezoid + circle=triangle then triangle-trapezoid=square. what is the missing shape and why

What is the measure of the smallest angle in the diagram? 15 29 32 45

Estimate the area under the curve f(x) = 16 - x^2 from x = 0 to x = 3 by using three inscribed (under the curve) rectangles. answer to the nearest integer.

The ordered pair (2,-5.2) is located in quadrant iv