1. The problem statement, all variables and given/known data Demonstrate what happens to X when a is doubled (a → 2a). a = tan^2(X) - 1/cos^2(X) 2. Relevant equations None given formally; Pythagorean Theorem - sin^2(θ) + cos^2(θ) = 1 (added myself). 3. The attempt at a solution Divide through Pythagorean above to give: tan^2(θ) + 1 = 1/cos^2(θ) 1/cos^2(θ) = sec^2(θ). tan^2(θ) - sec^2(θ) = -1 From given equation, a = -1. Doubling a yields 2a. But tan^2(θ) - sec^2(θ) = -1 for all values of (θ) including X as given. Is my solution therefore that nothing happens to X if a is doubled, or does the solution not consist of using the pythagorean identity? All thanks appreciated.