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In a right-angled triangle, the sides and the angles are connected by three trigonometric ratios.
The three trig ratios are:
A quick way to remember this is to memorise the word
SOHCAHTOA
Example
Using trigonometry, calculate the angle θº to 3 sig. figs.
Answer
Label the sides adjacent, opposite and hypotenuse in relation to the angle θº.
The given sides are the adjacent and the hypotenuse.
SOHCAHTOA
The correct trig ratio is COS.
Set up the trig equation to get:
cos θ = 3/5 = 3 ÷ 5 = 0.6
θ = cos-1 (0.6)
θ = 53.1º (3 s.f.)
