Purpose
To compute the coefficients c and s (c^2 + s^2 = 1) for a modified
hyperbolic plane rotation, such that,
y1 := 1/c * x1 - s/c * x2 = sqrt(x1^2 - x2^2),
y2 := -s * y1 + c * x2 = 0,
given two real numbers x1 and x2, satisfying either x1 = x2 = 0,
or abs(x2) < abs(x1).
Specification
SUBROUTINE MA02FD( X1, X2, C, S, INFO )
C .. Scalar Arguments ..
DOUBLE PRECISION X1, X2, C, S
INTEGER INFO
Arguments
Input/Output Parameters
X1 (input/output) DOUBLE PRECISION
On entry, the real number x1.
On exit, the real number y1.
X2 (input) DOUBLE PRECISION
The real number x2.
The values x1 and x2 should satisfy either x1 = x2 = 0, or
abs(x2) < abs(x1).
C (output) DOUBLE PRECISION
The cosines c of the modified hyperbolic plane rotation.
S (output) DOUBLE PRECISION
The sines s of the modified hyperbolic plane rotation.
Error Indicator
INFO INTEGER
= 0: succesful exit;
= 1: if abs(x2) >= abs(x1) and either x1 <> 0 or x2 <> 0.
Further Comments
NoneExample
Program Text
NoneProgram Data
NoneProgram Results
None