Can someone explain to me this :

Question

-sinx=cosx
X=3pi/4 and 7pi/4

Answer 1

- sin x = cos x

Divide both sides by - cos x

- sin x / - cos x = cos x / - cos x

tan x = - 1

Solution:

x = pi * n - pi / 4

If n = 1 then:

x = pi * n - pi / 4 = pi * 1 - pi / 4 = pi - pi / 4 = 4 pi / 4 - pi / 4 = 3 pi / 4

If n = 2 then:

x = pi * n - pi / 4 = pi * 2 - pi / 4 = 2 pi - pi / 4 = 8 pi / 4 - pi / 4 = 7 pi / 4