Q. 6

# Prove that [Hint: Express L.H.S. To prove: As equation on RHS is a simplified expression, so we must opt Left side equation and simplify it further so that we can get

LHS = RHS.

And thus we will be able to prove it.

LHS = By seeing the expression we can think that the problem can be solved using transformation formula:

By transformation formula, we have:

2 cos A cos B = cos(A + B) + cos (A – B)

-2 sin A sin B = cos(A + B) - cos (A – B)

Or cos A – cos B = But as LHS expression does not contain ‘2’ in its term. So we multiply and divide the expression by 2.

LHS = Applying transformation formula, we have –

LHS = LHS = LHS = { cos (-x) = cos x}

LHS = Again, applying the transformation formula:

LHS = LHS = LHS = sin 4θ sin = RHS

Hence: Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos  Trigonometric Functions - 0152 mins  Conditional Identities31 mins  Trigonometric Functions - 0568 mins  Trigonometric Functions - 0366 mins  Trigonometric Functions - 0658 mins  Trigonometric Series45 mins  Interactive Quiz on trigonometric ratios & identities73 mins  Trigonometric Functions - 0268 mins  Trigonometric Functions - 0466 mins  Trigonometric Functions - 0865 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation view all courses 