Answer:
b. sin or csc
Step-by-step explanation:
Remember that sine trigonometric function is the ratio of the opposite side of a right triangle to its hypotenuse; in other words:

Also, the cosecant is the inverse of sine, so:

Now, for our triangle, our angle is 27°, the longest side of it is TS, and the opposite side of our angle (27°) is TR; therefore,
,
, and
.
Replacing values:
- Using the sine trigonometric function






- Using the cosecant trigonometric function





We can conclude that we can use either the sine trigonometric function or the cosecant trigonometric function to solve the problem.