18. Find all the trigonmetric functions of a. 2 5 (a) sin(a) = (b) cos(a) = (c) tan(a) = (d) sec(a) = (e) csc(a) = (f) cot(a) = 19. Using your answer above, find sin(tan '(?)) 20. More generally, find sin(tan - (I)) 21. For the same o above, find cos(20)