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Many of the applications of physics will require you to have a thorough knowledge of the basic properties of right triangles, i.e., triangles that have one angle equal to 90°.
The trigonometric functions are defined with respect to a right triangle as follows:
sin θ = y/r
cos θ = x/r
tan θ = y/x
The values of the trigonometric sine, cosine, and tangent functions for a given θ can be determined from a table such as in the appendix to your text or the last page of this module. You can also get the values by use of most slide rules ("S" and "T" scales) and many electronic calculators.