For this case what you should do is find the value of each of the functions and compare it with the value of sin 75.
The function that has the same value of sin 75 is cos 15
sin 75 = cos 15 = 0.97
Also by trigonometry you can find the answer.
Notice that 90-75 = 15, therefore, sin 75 = cos 15
answer
cos 15
