How to evaluate/simplify numerical expressions inside a symbolic expression?

[thilgendorf]

I've attached an image of my work below. It seems like it should be very simple to have Mathcad evaluate the expressions highlighted in red so that the entire matrix is much simpler. But I've tried all the symbolic keywords and none of them seem to work. What am I missing?

[AndyWesterman · Accepted solution]

Try replacing the 90*deg with pi/2 as below:

The symbolic evaluation isn't too good with units , so treating it as just a number (radians) seems to help

Regards

   Andy

[thilgendorf]

That worked! Thank you!

Interestingly, though, when I removed the "deg" unit and just had the variable equal to "90", it didn't work either. It had to be "pi/2".

[LucMeekes]

Because Mathcad's trig functions work only with radians.

You might have gotten 0.89399666 as a simplification of sin(90)...

[StuartBruff]

Just as a follow up to the explanations already given, the Symbolic Processor in Mathcad doesn't know anything about units and treats unit names as it would any other symbols - if they have a value, it evaluates them, otherwise it leaves them alone.   It is possible to use units with the Symbolic Processor by defining them yourself.  It is also possible to get the symbolic processor to return a decimal number result (if there is one) by using the "float" symbolic keyword or by writing one of the numbers in an expression as a decimal rather than as an integer or rational (eg, 90.0 rather than 90).

Stuart