# NCERT Class 11-Math's: Exemplar Chapter 3 Trigonometric Functions Part 10

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**Question 6:**

Prove that

**Answer:**

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.

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

By transformation formula, we have:

But as LHS expression does not contain ‘2’ in its term. So we multiply and divide the expression by 2.

Applying transformation formula, we have –

Again, applying the transformation formula:

Hence:

**Question 7:**

**Answer:**

Given,

Squaring and adding equation 1 and 2, we get –

Using: , we get –

**Question 8:**

Find the value of tan ’.

**Answer:**

**Question 9:**

**Answer:**

As we know that-

From T-ratios of multiple angle, we know that

Hence: