Question

The sides of right triangle ABC have lengths 12ft, 16ft, and 20 ft. Which could be the cosine of angle C? 
A. 3/5 
B. 5/4 
C. 4/3 
D. 5/3

Answer 1

The triangle ABC is

 

Side a = 12 ft, b = 16 ft and c = 20ft then angle C is the angle opposite of the 20 ft

 

then angle C is 90° and cos(90°) = 0°

However cos(A) = adjacent side / hypotenuse = 16/20 = 4/5,

 

cos(B) = 12/20 = 3/5 and cos(C) = 12/20 = 3/5.
 
So the only possible valid answer is A.