How do I prove the identities of these questions? 1+tan2u1−tan2u=1cos2u−sin2u sinx+sin(5x)cosx+cos(5x)=tan(3x)
How do I prove the identities of these questions?
Answer & Explanation
You will need two facts, first the definition of tangent, second main trigonometric identity:
Using that you may transform (1) as:
The original (2) which is:
is false as shown in another answer (take for instance). Here is a visualization of LHS and RHS