Simplify
\[\cos ^2 x + \cos^2 (x + y) - 2 \cos x \cos y \cos (x + y).\]
Question:
Simplify
\[\cos ^2 x + \cos^2 (x + y) - 2 \cos x \cos y \cos (x + y).\]
Answer:
Let's think step by step.

user
\sin^2 y
Simplify
\[\cos ^2 x + \cos^2 (x + y) - 2 \cos x \cos y \cos (x + y).\]
train