Show Menu

Trigonometry In Triangles Cheat Sheet (DRAFT) by

Cheat sheet for Trig in triangles

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Special Ratios

Sine Rule: a / SinA = b / SinB = c / SinC

Cosine Rule (Gives us the 3rd side): a2 = b2 + c^2 - 2bcCosA


Cosine Rule (Gives us the angle's size): = CosA = b2 + c2 - a^2 / 2bc

Area Rule (Same as Cosine Rule BUT cannot use it with "3rd side" condit­ion!): 1/2 x abSinC

Angles of Elevation & Depression

- The dotted lines are seen as stg. lines, therefore 90 degrees can be between it & another line!
- Parallel lines appear often so look out for those! ( Z, F U )
NB the following reason: Angles on a stg. line
NB the following reasons: Angles in a triangle

Normal Ratios

Sinθ = Opp./Hyp.
Cosθ = Adj./Hyp.
Tanθ = Opp./Adj.
Soh Cah Toa