atan(x): Trigonometric ArcTangent¶

Trigonometric arctangent (inverse arctangent) function.

Declaration¶

Syntax¶

retval = atan(x)
elemental real(p) function atan(x)
elemental complex(p) function atan(x)

Arguments¶

x the input value, can be real or complex; less than or equal to 1.

Return values¶

The returned value has the kind of the input value and TYPE may be real or complex.

Description¶

atan(x) computes the arctangent of the argument x.

The arc tangent is the inverse function of the arctangent function. It is commonly used in trigonometry to find the angle when the lengths of the opposite side of a right triangle and base are known, i.e., perpendicular and base length.

Types¶

Supported argument types float, double, complex float, complex double.

interface atan
    module procedure satan, datan, catan, zatan
end interface

contains

interface
    elemental real(sp) function satan(x)
    real(sp), intent(in) :: x
    end function

    elemental real(dp) function datan(x)
    real(dp), intent(in) :: x
    end function

    elemental complex(sp) function catan(x)
    complex(sp), intent(in) :: x
    end function

    elemental complex(dp) function zatan(x)
    complex(dp), intent(in) :: x
    end function
end interface

Examples¶

program intrinsics_atan
implicit none
integer, parameter :: arg_x = kind(0.0)
real(arg_x) :: x1
real :: retval_x
real :: arg_x
retval_x = atan(0.84147098)
print *, ret_val_x
retval_x = atan(x1)
print *, ret_val_x
end program

Result:

0.699521642
0.699521642