Recall:
The tan of the measure of an angle is the ratio of the opposite side to the adjacent side to that angle, that is :
[tex]\displaystyle{ \tan x^{\circ}= \frac{opposite\ side}{adjacent \ side} [/tex].
Since this ratio is 3/y, we denote the opposite side, and adjacent side respectively by 3 and y.
(Technically we should write 3t and yt, but we try our luck as we see y in the second ratio too!)
Similarly, [tex]\displaystyle{\cos x^{\circ}= \frac{adjacent\ side}{hypothenuse} [/tex].
The adjacent side is already denoted by y, so we denote the length of the hypotenuse by z.
Now the sides of the right triangle are complete.
[tex]\displaystyle{ \sin x^{\circ}= \frac{opposite\ side}{hypotenuse}= \frac{3}{z} [/tex]
Answer: A
