Lessons · Quantitative Reasoning
CLT Quantitative Reasoning · Lesson
Trigonometry
In a right triangle, sine = opposite ÷ hypotenuse, cosine = adjacent ÷ hypotenuse, tangent = opposite ÷ adjacent (SOH CAH TOA).
- Label the sides from the angle you are working with: opposite, adjacent, hypotenuse.
- Choose the ratio that uses the sides you know and the one you want.
- Remember sin θ = cos(90° − θ): the sine of one acute angle is the cosine of the other.
Q. A right triangle has sides 5, 12 and 13. What is the sine of the angle opposite the side of length 5?
Answer 5/13
Opposite is 5, hypotenuse is 13. The cosine of the same angle is 12/13.
- Labeling opposite and adjacent from the wrong angle.
- Using the hypotenuse in a tangent.
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