## Introduction

## Process

**Task 1: Recap on acute angles**

**Step 1:**

Watch the following youtube video.

**Task 2: Obtuse Angles**

**Step 1: Extend the definition of ****trigonometric ratios.**

**Question 1: **

What will cosine theta and sine theta be if the circle is of radius *r* instead?

**Step 2:**

Do the Investigation on page 175 in your textbook.

**Question 2:**

What can you conclude from the Investigation?

**Step 3:**

Look at the Conclusion tab for the answers of Question 1 and 2. Do Practise Now 1 and 2 in your notebook.

**Step 4:**

Give yourself a pat on the back. You have completed your elearning! :D

## Conclusion

**Question 1**

**Answer: **cosine theta = x/r and sine theta = y/r

**Question 2**

**Answer: **sin A = sin (180-A) and cos A = -cos (180-A)