Calculators Troubleshooting Simultaneous Equations with Trigonometric Functions on TI-89

[dlikes]

Homework Statement

My problem is getting the SOLVE() function to work correctly. I have used it plenty of times in the past, but when I put in these 4 equations to solve simultaneously, it gives me the wrong answers. My Professor said that TI-89's sometimes have problems when having to solve trig functions, like solving for theta, gamma, phi, etc., inside of simultaneous equations.

The problem had me break it up into 2 Free Body Diagrams.

here are the exact 4 equations that I have:

1st free body Diagram:
Sum of Forces in the X direction:
CB*cos(theta)-CD*cos(30)=0
Sum of Forces in the Y direction:
-CB*sin(theta)+CD*sin(30)-30=0

2nd free body diagram:
Sum of forces in X direction:
-CB*cos(theta)+BA*cos(45)=0
Sum of forces in Y direction:
CB*sin(theta)+BA*sin(45)-60=0

The Variables I have to solve are:CD,CB,BA,Theta.
The correct answers are:
BA=80.7 lb
CD=65.9 lb
CB=57.1 lb
Theta=2.95 degrees.

The Professor verified that my equations were right. Please if anyone could help me with this, it would seriously be a breakthrough for me. Thanks!

 

[dlikes]

OK, i must have punched something in wrong, because it worked out perfectly this last time I tried it.