Terminology

The trigonometric ratios are used with right triangles and relate an angle of the triangle to the ratio of two sides.  When determining a trig ratio, look at the triangle from the point of view of the given angle.  The greek symbol θ is one symbol used to mark the given angle.  Relative to that angle there is an adjacent side and an opposite side.  The adjacent side is the leg of the triangle that makes one side of the given angle.  The opposite side is the leg of the triangle that does not form a side of the given angle.  The hypotenuse is always the side opposite the 90o angle. 

Trig Ratio Triangle

It is very important that these relationships are understood when working with the ratios.

 

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