👉 Learn how to verify trigonometric identities involving the addition and subtraction of terms. To do this it is usually ...

👉 Learn how to verify Pythagoras trigonometric identities. A Pythagoras trigonometric identity is a trigonometric identity ...

Sec(a-b) = cos(a+b) / cos^2a - sin^2b I'm trying to prove this, by turning the left side into the right. I am stuck. Presumably you have already done the sum and difference formulas for sin and cos.