Question

For this right triangle, what is the cosine of angle C?

A) 12/13
B) 13/12
C) 5/12
D) 5/13
50 points, again by 5 pm.
after I completed the activity, I will go through any questions I may have needed help with and Mark those who were correct.​

Answer 1

A cos C = 12/13

Explanation:

cos theta = adjacent side/ hypotenuse

cos C = BC/AC

But we don't know BC, but we can find it using the Pythagorean theorem

a^2 +b^2 = c^2

5^2 +BC^2 = 13^2

25 + BC ^2 =169

Subtract 25 from each side

BC^2 = 169-25

BC ^2 = 144

Taking the square root of each side

BC =12

cos C = 12/13