In calculus it is often desired to replace radial expressions with trigonometric expressions The next group of exercises illustrates this Simplify the given expression as much as possible by making the given substitution Assume 0 0 90 65 Vx 9 x 3 tan 0 66 V 16 x 4 tan 0 67 36 x x 6 sin 0 69 Vx 25 x 5 sec 0 5 71 V4x 25 x tan 0 73 V16 9x x 4 3 sin 8 68 V100x x 10 sin 70 Vx 49 x 7 sec 0 72 9x 1 x tan 8 74 V10 x x 10 sin 8