Symbolic problem in quad() function

function f=fun(t)
syms c1 ..... c18
f=(1./5.*cos(c1+c2.*t+c3.*t.^2+c4.*t.^3)+3./5.*cos(c1+c2.*t+c3.*t.^2+c
4.*t.^3+c9+c10.*t+c11.*t.^2+c12.*t.^3)-3./20.*sin(2.*pi.*t)).^2;
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I have an equation with the symbolic variables c1...c18. It's not
integrated by the int() command symbolicly. When I tried the quad
function i have encountered with this error.
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Function 'isfinite' is not defined for values of class 'sym'.
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How can i integrate this function by numerically or symbolicly.
Please help.
.

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