Precalc Trig Functions

Question

cos(x)=7/25

3∏/2 < x < 2∏ and

sin(y)=4/5

∏/2 < y < ∏

(∏= pi)

Find:

a) sin(x)

b) cos(y)

c) cos(x-y)

d) sin(x+y)

e) sin(2x)

f) cos(2y)

Answer 1

x = arcCos(7/25) = 73.74° but is 3∏/2 < x < 2∏, so x = -73.74°

sin(y)=4/5 y = arcSin(4/5) = 53.13° but ∏/2 < y < ∏ so y = 143.13°

a) sin(x) = -.96

b) cos(y) = -.8

c) cos(x-y) = -.8

d) sin(x+y) = .352

e) sin(2x) = -.5376

f) cos(2y) = .280