Answer:
Explanation:
Given: ΔDEF is a right angled triangle, right angled at E, DE=21, DF=75 and EF=72.
To find: The trigonometric ratio for cosD.
Solution: We are given that ΔDEF is a right angled triangle, the value of angle of cos is given as:

In the given figure, corresponding to the angle D, the base is DE that is equal to 21 and the hypotenuse is DF that is equal to 75.
Therefore,


Thus, the trigonometric ratio for cosD is
.