Futurebasic/Language/Reference/atn

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radianAngle# = atn( expr )

Returns the arctangent of expr in radians. In other words, if expr represents the tangent of some angle, then atn(expr) returns the angle. The returned angle will be in the range of -π/2 to +π/2 radians (which corresponds to -90 to +90 degrees). atn always returns a double-precision result.

Because atn(1) equals π/4, you can use atn to get a value for π.

dim pi#
end globals

pi = atn( 1 ) * 4
print pi

Program output:

3.14159265359

No special notes.

sin; cos; tan; asin; acos; atan

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