(10) One way to define the trigonometric functions sin, cos is as follows: . Consider the unit circle x2 + y? = 1, and a point (x, y) on the unit circle. . As in the diagram below, each point (x, y) corresponds to an angle 0 (measured counter- clockwise from the positive r-axis.) . We define sin 0 = y: the y-coordinate of the corresponding point on the unit circle. . We define cos 0 = x: the x-coordinate of the corresponding point on the unit circle. Prove the following trig identities using this definition and elementary geometry: you may not use other trig identities or definitions of sin, cos. cos2 0 + sin2 0 = 1 cos(-0) = cos(0) sin(-0) = - sin(0)