Trig ratios can be remembered with the phrase SOH CAH TOA.
Sine: Opposite/Hypotenuse.
Cosine: Adjacent/Hypotenuse
Tangent: Opposite/Adjacent.
In this triangle, the adjacent side to angle R (the side touching the angle) is 12 cm, the opposite side (the side farthest away) is 5 cm, and the hypotenuse (the longest side) is 13 cm.
So, filling in the measurements with the correct SOH CAH TOA ratios results in:
tan R = 5/12
cos R = 12/13
sin R = 5/13
