The cosine of an angle on a right triangle is the ratio of the adjacent leg to the hypotenuse. The cosine of one angle subtracted from another can be determined by means of a very simple formula. This formula assumes that you are working with two right triangles, one of which has an angle you are calling α, and the other with an angle known as β. The legs of each triangle are known as a and b, and the hypotenuse is labeled c.
Instructions
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1
Divide b by c to find the cosine of angle α. Divide a by c to find the sine of α. Repeat on the second triangle to find the sine and cosine of β.
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2
Multiply the cosine of α by the cosine of β. Multiply the sine of α by the sine of β.
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3
Add the two results of Step 2 together to obtain the solution to the equation cos(α - β).