Maths P3 help!!

[ShreeyaBeatz]

Guys im stuck here. Please help me. For your easiness I've attached the picture of the question!!

 

[mixinmao]

Don't complicate the question. You did great up to the 0 = cosx + sinx but the following steps are confusing.
My way:
0 = sinx + cosx
-sinx = cosx
-sinx/cosx = 1
-tanx = 1
tanx = -1
x = tan^1(-1) = -45 degree or -1/4*pi