SAT Right Triangles and Trigonometry study notes

Start by identifying the right angle. The side across from it is the hypotenuse and must be longest. Use a² + b² = c² for lengths; for a chosen acute angle, sine is opposite over hypotenuse, cosine is adjacent over hypotenuse, and tangent is opposite over adjacent.

Worked example

In the right triangle, the side opposite angle θ is 7 and the hypotenuse is 25. What is cos θ?

First find the adjacent leg: 25² − 7² = 576, so it is 24. Cosine is adjacent over hypotenuse, giving cos θ = 24/25. The diagram tells you which acute angle θ names.

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