ACOS( )

Topic group Related topics

Returns the inverse cosine (arccosine) of a number.

Syntax

ACOS(<expN>)

<expN>

The cosine of an angle, from –1 to +1.

Description

ACOS( ) returns the radian value of the angle whose cosine is <expN>. ACOS( ) returns a number from 0 to pi radians. ACOS( ) returns zero when <expN> is 1. For values of x from 0 to pi, ACOS(y) returns x if COS(x) returns y.

To convert the returned radian value to degrees, use RTOD( ). For example, if the default number of decimal places is 2, ACOS(.5) returns 1.05 radians while RTOD(ACOS(.5)) returns 60.00 degrees.

Use SET DECIMALS to set the number of decimal places ACOS( ) displays.

To find the arcsecant of a value, use the arccosine of 1 divided by the value. For example, the arcsecant of 2 is ACOS(1/2), or 1.05 radians.