The answers are given below:
What is Trigonometry?
Trigonometry is a branch of mathematics that studies relationships between the sides and angles of triangles.
1. (cos x. cos y)(tan x + tan y) = sin (x+ y)
(cos x. cos y)(tan x + tan y)
= cos x. cos y (sinx/ cos x + sin y/ cos y)
= sin x cos y + sin y cos x
= sin (x+ y) [ sin ( x +y)]= sin x cos y + sin y cos x
= RHS
3. [tex]-\sin ^2\left(x\right)-\cos \left(2x\right)=0[/tex]
Using identity
[tex]-\cos ^2\left(x\right)=0[/tex]
cos ² x=0
Applying [tex]x^{n} =0[/tex] then x=0
So, cos x =0
General solution will be [tex]x=\frac{\pi }{2}+2\pi n,\:x=\frac{3\pi }{2}+2\pi n[/tex].
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