IDE with cos() in the integral

[pollinico]

I would like to have an integral equation as follows:

def ide(inputs, outputs, int_mat):
    x = outputs[:, :1]
    theta = outputs[:,3:4]
    ...
    ide1 = x - tf.matmul(int_mat, cos(theta))

I am having issues, I think because of cos(theta), where cos=tf.math.cos.
Do you have ideas what is the issue or if this type of IDE could work in DeepXDE?
Thank you!