Trig Notes (MAT101)

Simple Notes to Learn Trig:

  1. You are going to need to remember:

SOH - Sin = Opp/Hyp

CAH - Cos = Adj/Hyp

TOA - Tan = Opp/Adj

Opposite = Side across from the angle

Adjacent = The side next to the angle

Hypotenuse = The longest side

So start with labeling the triangle!



  1. Find a side.

Pick the formula from SOH, CAH, TOA - Then rearrange.

If the unknown side is on top

Side = known side x trig (angle)

EXAMPLES:
Opp = Hyp x sin(0)

Adj = Hyp x cos(0)

Opp = Adj x tan(0)

If the unknown is on the bottom

Side = known side / trig (angle)

EXAMPLES:

Hyp = Opp / Sin(0)

Hyp = Adj / Cos(0)

Adj = Opp / Tan(0)



  1. Finding the angle

0 = sin-1 (O/H)

0 = cos-1 (A/H)

0 = tan-1 (O/A)

Just put the fraction into the calculator, press the right inverse button & DONE!



What if I want to find the angle?

If you have all 3 sides use ratios to find the angle

You always USE inverse trig to find the angle

  1. Label the triangle

  2. Pick the correct ration (SOH, CAH, TOA)

  3. Put the fractions into inverse (Whichever one matches your two sides use)