Microsoft® Excel® 2010 Formulas & Functions Inside Out

COS()

Syntax. COS(number)

Definition. This function returns the cosine of a number.

Argument

• number (required) The angle in radians for which you want the cosine

Background. In a right triangle, the ratio between the adjacent leg and the hypotenuse depends on the apex angle (see Figure 16-10). The ratio between the adjacent leg of an angle and the hypotenuse is the cosine (cos) of the angle.

Figure 16-10. Aspect ratios in a right triangle.

If angle α in an unit circle (c = 1) increases between 0° and 90°, the cosine decreases between 1 and 0 (see Figure 16-11 ...