# NCERT Class 12-Mathematics: Chapter –5 Continuity and Differentiability Part 17

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**Question 55:**

**Answer:**

We have,

By the rules given below:

Chain Rule

Product rule:

On differentiating both sides with respect to , we get

**Question 56:**

**Answer:**

We have,

On differentiating both sides with respect to , we get

**Question 57:**

**Answer:**

**Question 58:**

If , then show that

**Answer:**

Given:

Differentiating the above with respect to , we get

Now, we again differentiate with respect to y, we get

Hence Proved