We have 3 ways to solve trigonometric problem, using primary trigonometric ratio, sine law and cosine law.
- Using Primary Trigonometric Ratio (SOH CAH TOA)
– When the triangle have a right angle 
- Using Sine Law (sin A/a = sin B/b = sin C/c)
– In non-right triangles
– one complete pair of a known angle and its opposite side, and one other angle or side.
- Using Cosine Law (C2=b2+a2-2ab cosC)
– When the triangle have 2 sides and contained angle 
In grade 10, I only learnt how to solve basic trigonometric problem which used trig formula, SOH CAH TOA. Now, in Pre-calculus 11, I learnt two more trig formula, sine law and cosine law which is more convenient for us to solve trig problems.