Y prime equals 9. Remember the derivative of secon X is secant tangent, so Y prime is 9, secon X tangent XY double prime. We have to take the nine times the derivative of the secon X which is secant tangent times the tangent. Plus, by the product rule 9 secon X times the derivative of tangent X, which is secant squared X. So we get 9 secant X tangent squared X + 9 secant cubed X. By our Pythagorean identity, we know that secant squared X is really no, sorry. By our Pythagorean identity, we know that tangent squared X is really just secant squared X -, 1. So when we distribute the 9 secant X, we get 9 secant cubed X -, 9 secant X + 9 secant cubed X. We get 18 secant cubed X -, 9 secant X.