# Thread: solution to trig

1. ## solution to trig

determine the fundamental solution set of sin x = sin 5x

2. Originally Posted by maeca
determine the fundamental solution set of sin x = sin 5x
Case 1: $\displaystyle 5x = x + 2 n \pi$.

Case 2: $\displaystyle 5x = (\pi - x) + 2 n \pi$.

Solve for x in each case.

3. ## sin cos

is sinA + sin B = 2 sin ((A+B)/2) cos ((A-B)/2)

4. Originally Posted by maeca
is sinA + sin B = 2 sin ((A+B)/2) cos ((A-B)/2)
Yes. And I know what you're thinking. That's another way of solving the problem.

But the relevant formula for this question is

sinA - sin B = 2 sin ((A-B)/2) cos ((A+B)/2)

5. ## tangent

i would like to ask another question.
how can i express tan x/(1-2sin x + 3 cos x) in terms of tan(x/2)
thanks for answering my questions...

6. Originally Posted by maeca
i would like to ask another question.
how can i express tan x/(1-2sin x + 3 cos x) in terms of tan(x/2)
thanks for answering my questions...
Read this: PlanetMath: Weierstrass substitution formulas

By the way: Questions unrelated to the original questions should be posted as a new thread.