# Activity for cos(a+b) formula

- Author:
- Gary Rubinstein

## Question 1

Which segment is ?

## Question 2

Which segment is ?

## Question 3

Which segment is ?

## Question 04

Which segment is ?

## Question 5

Which segment is ?

## Question 6

Which segment is ?

## Question 7

What is an expression in terms of and for the length of AB? Hint: Use right triangle ABG.

## Question 8

Explain why angle CAD must be congruent to angle GEF?

## Question 9

Write an expression in terms of and for the length of FG? Hint: Use right triangle EFG

Select all that apply

- A

## Question 10

In question 5, you should have found that segment AI can be called But AI is also the difference of AB-IB=AB-FG. What is another (more complicated) expression for the length of AI?