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Estanislao · Joined: 19 Jun 2013 Posts: 3 Location: Spain

Hi everyone,

I was refreshing FORTRAN 95 and I had a problem with SIN and ASIN. I think both problems are related

The first problem is when I try to calculate the sin 45(radians). The calculator gives me 0.70 while Plato gives 0.85.

The other problem is with ASIN. My program does not calculate the ASIN. This is my program:

PROGRAM cap1_7

IMPLICIT NONE
REAL :: A,B,S,pi,C
REAL :: X,Y,T
WRITE(*,*)'Sides of a triangle (m)'
READ(*,*)A,B
pi=3.1416
S=A*B
C=SQRT(A**2+B**2)
T=A/C
X=ASIN(T)
Y=(180-90+X)

PRINT*, 'hypotenuse',C,'m'
PRINT*, 'Area of rectangle',S,'m'
PRINT*, 'Triangle angles',X,Y,'Radians'

END PROGRAM cap1_7

Thanks in advance

Wilfried Linder · Posted: Thu Mar 27, 2014 7:49 pm Post subject:

This code works on my PC:

davidb · Joined: 17 Jul 2009 Posts: 560 Location: UK

First of all SIN 45 degrees = 0.70 and SIN 45 radians = 0.85 (approx).

Therefore you probably have your calculator in degrees mode, not radians.

And second, in your code X is one of the angles in the triangle and is in radians, the other angle Y should be obtained by Y = (3.14159/2.0) - X. That is subtract from PI/2 not from 90 degrees (also you have Y = 90 + X so there is also the wrong sign in there!).

Or use,

Estanislao · Joined: 19 Jun 2013 Posts: 3 Location: Spain

Linder and david thanks for all. Next time I will be careful with the units