# NCERT Class 11-Math's: Exemplar Chapter 3 Trigonometric Functions Part 4

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**Question 5:**

Find the value of

**Answer:**

We have

(1)

Also

(2)

Similarly, (3)

Using (2) and (3) in (1), we get

**Question 6:**

Prove that

**Answer:**

We have

**Question 7:**

Solve the equation

**Answer:**

We have

Or

Or

Or

Or

When

When

Which gives

All these values of are contained in . Hence, the required solution set is given by

**Question 8:**

Solve

**Answer:**

Here,

Which gives

If we take

Again, if we take

Therefore, the possible solutions of above equations are

## Long Answer Type

**Question 9:**

Find the value of

**Answer:**

Write