### Video Transcript

Write an expression equivalent to
cos squared π-fourths minus sin squared π-fourths.

There is a trig identity that
states cos squared π minus sin squared π is equal to cos of two π. And looking at our expression, π
over four can replace π, which would mean we would know what this is equal to
because we can replace π with π divided by four. And this can simplify. The two can go into the four two
times.

So we get the cos of π over
two.