# NCERT Class 12-Mathematics: Chapter – 2 Inverse Trigonometric Function Part 13 (For CBSE, ICSE, IAS, NET, NRA 2022)

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**Question 18**:

Show that and justify why the other value is ignored?

**Answer**:

LHS

Using quadratic formula

Since,

But . So this value is ignored.

**Question 19**:

If is an arithmetic progression with common difference , then evaluate the following expression

**Answer**:

Given That: