# Compute trig. function in symbolic matrix

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Sam Ade on 30 Oct 2015
Commented: Walter Roberson on 30 Oct 2015
Hi,
I have a symbolic matrix (as shown below). I would like for matlab to compute the trig functions with non-th5 values. How do I go about this.
[ cos(th5), -sin(th5), 0, 0]
[ cos(90)*sin(th5), cos(90)*cos(th5), -sin(90), 0]
[ sin(90)*sin(th5), sin(90)*cos(th5), cos(90), 0]
[ 0, 0, 0, 1]

Walter Roberson on 30 Oct 2015
Are you referring to reducing the sin(90) and cos(90) to the corresponding constant values? Because if you are then you need to take into account that sin() and cos() operate in radians, not in degrees. But this is your purpose then vpa() the symbolic matrix.
If you are wanting to substitute a numeric value for th5 then use subs(), possibly in conjunction with vpa() or double()
subs(TheMatrix, th5, 1.238343) %put in a particular numeric value
##### 2 CommentsShowHide 1 older comment
Walter Roberson on 30 Oct 2015
You can call sind() or cosd() in a symbolic expression, provided it is at the MATLAB level (not in a string that has been passed to solve() or the like.)

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