Let's simplify the given expression step by step:

We know that sin^2(x) + cos^2(x) = 1
Therefore, sin^2(53) = 1 - cos^2(53)

Substituting this into the expression:
(1 - cos^2(53) - cos^2(53))/(cos 106)

Simplifying further:
(1 - 2cos^2(53))/(cos 106)

Since cos 106 = -cos(74) (because cosine is negative in the second and third quadrants):
(1 - 2cos^2(53))/(-cos 74)

Using the Pythagorean identity cos^2(x) = 1 - sin^2(x):
(1 - 2(1 - sin^2(53)))/(-cos 74)

Simplifying again:
(1 - 2 + 2sin^2(53))/(-cos 74)
(-1 + 2sin^2(53))/(-cos 74)

Therefore, the simplified expression is (-1 + 2sin^2(53))/(-cos 74)