Use SOH-CAH-TOA method and figure out which sign you need. SOH- Sin, CAH- Cos, TOA- Tan.
Also,
SOH- opposite/hypotenuse
CAH- adjacent/hypotenuse
TOA- opposite/adjacent
Look at the angle and see which terms you have already. For example, if you had opposite the angle and the adjacent side, you would choose tangent because its TOA. Hope that helps!
