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