## anonymous one year ago In triangle ABC, a = 3, b = 5, and c = 7. Find the approximate value of angle A. a. 22° b. 38° c. 142° d. 158°

1. anonymous

@amoodarya can you help please?

2. amoodarya

use law of cosine

3. anonymous

i dont remember how to do that

4. amoodarya

$b^2+c^2-a^2=2bc \cos(A)$ put a,c,b in formula you will find cos(A)

5. anonymous

5^2+7^2-3^2=70cos a

6. anonymous

A=22