You won't necessarily have to know that, but you could get a question like this.
In the experiment, it was observed that Material VI had an average threshold angle 72 degrees. We find that mustatic is equal to the tangent of the threshold angle. What is the approximate mustatic for Material VI against the ramp?
Knowing the exact tangent is pointless, but being able to deduce the approximate tangent (to eliminate the wrong answers) is helpful. Tangent = sin/cos, so for the three common angles you should know that tan 30degrees = 0.5/0.86, tan 45degrees = 0.71/0.71, and tan 60degrees = 0.86/0.5. Solving for tan 60degrees, we get 1.72. For an angle greater than 60degrees, the tangent will be larger than 1.72. Only choice D fits that restriction, so it must be the answer.
So while knowing the exact value of tangent 72degrees is fruitless, knowing that it is greater than 1.72 and being able to think through a multiple choice question is helpful. If you don't like the way a question is worded (i.e., think that it's unrealistic), then rewrite your own question using the information in a more applicable way.