Question

Given the right △△DEF, DE = 30, EF = 72 and DF = 78. Find the cos F=

Answer 1

The other person that answered should be right

Answer 2

see the figure below to better understand the problem

cos(F)=EF/DF --------> by CAH

substitute given values

cos(F)=72/78

simplify

cos(F)=12/13

Option C