Setting a function to an expression that resulted from a SOLVE function
Subject: Setting a function to an expression that resulted from a SOLVE function
From: Craig Ugoretz
Date: Mon, 13 Sep 2004 22:02:11 -0700 (PDT)
In the code below, I create the triangle equation and label it TRI. I
then solve TRI for THETA in order to rearrange the equation in terms
of THETA. I then create a function THETA(A,B,C) and try to set it
equal to the solution of the above. When I try make substitutions for
the arguments of THETA, however, the function does not evaluate
numerically. Why? Also, THETA(x,y,z) results in D4. Why?
(C1) TRI: C^2 = A^2+B^2-2*A*B*COS(THETA);
2 2 2
(D1) C = - 2 A B COS(THETA) + B + A
(C2) THETA(A,B,C):= RHS(FIRST(SOLVE(TRI,THETA)));
(D2) THETA(A, B, C) := RHS(FIRST(SOLVE(TRI, THETA)))
(C3) THETA(A,B,C);
SOLVE is using arc-trig functions to get a solution.
Some solutions will be lost.
2
C B A
(D3) %PI - ACOS(----- - --- - ---)
2 A B 2 A 2 B
(C4) THETA(1,2,3);
SOLVE is using arc-trig functions to get a solution.
Some solutions will be lost.
2
C B A
(D4) %PI - ACOS(----- - --- - ---)
2 A B 2 A 2 B
(C5) EV(THETA(1,2,3),NUMER);
SOLVE is using arc-trig functions to get a solution.
Some solutions will be lost.
RAT replaced -0.5 by -1//2 = -0.5
RAT replaced -3.14159265358979 by -103993//33102 = -3.1415926530119
2
0.5 C 0.5 B 0.5 A
(D5) - 3.020965500573983E-5 (33102 ACOS(------ - ----- - -----) - 103993)
A B A B