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Length of an arc between two angles: Difference between revisions
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<pre>
43.63323129985824
</pre>
=={{header|Fortran}}==
The Fortran subroutine contains the MAX(DIF, 360. - DIF) operation. Other solutions presented here correspond to different interpretations of the problem. This subroutine computes the length of the major arc, which is not necessarily equal to distance traveling counter-clockwise.
<lang fortran>*-----------------------------------------------------------------------
* given: polar coordinates of two points on a circle of known radius
* find: length of the major arc between these points
*
*___Name_____Type___I/O___Description___________________________________
* RAD Real In Radius of circle, any unit of measure
* ANG1 Real In Angle of first point, degrees
* ANG2 Real In Angle of second point, degrees
* MAJARC Real Out Length of major arc, same units as RAD
*-----------------------------------------------------------------------
FUNCTION MAJARC (RAD, ANG1, ANG2)
IMPLICIT NONE
REAL RAD, ANG1, ANG2, MAJARC
REAL FACT ! degrees to radians
PARAMETER (FACT = 3.1415926536 / 180.)
REAL DIF
* Begin
MAJARC = 0.
IF (RAD .LE. 0.) RETURN
DIF = MOD(ABS(ANG1 - ANG2), 360.) ! cyclic difference
DIF = MAX(DIF, 360. - DIF) ! choose the longer path
MAJARC = RAD * DIF * FACT ! L = r theta
RETURN
END ! of majarc
*-----------------------------------------------------------------------
PROGRAM TMA
IMPLICIT NONE
INTEGER J
REAL ANG1, ANG2, RAD, MAJARC, ALENG
REAL DATARR(3,3)
DATA DATARR / 120., 10., 10.,
$ 10., 120., 10.,
$ 180., 270., 10. /
DO J = 1, 3
ANG1 = DATARR(1,J)
ANG2 = DATARR(2,J)
RAD = DATARR(3,J)
ALENG = MAJARC (RAD, ANG1, ANG2)
PRINT *, 'first angle: ', ANG1, ' second angle: ', ANG2,
$ ' radius: ', RAD, ' Length of major arc: ', ALENG
END DO
END
</lang>
{{out}}
<pre> first angle: 120.000000 second angle: 10.0000000 radius: 10.0000000 Length of major arc: 43.6332321
first angle: 10.0000000 second angle: 120.000000 radius: 10.0000000 Length of major arc: 43.6332321
first angle: 180.000000 second angle: 270.000000 radius: 10.0000000 Length of major arc: 47.1238899
</pre>
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