The Goal

Find

The Mistake

Find the mistake:

(Roll the mouse over the math to see a hint in red)

The Correction

(Roll the mouse over the area above to see the correction in blue)

An Explanation

The student has not learned the correct derivative formula for inverse tangent (the formula in the mistake is either close to the derivative of the inverse secant, or is actually the derivative of inverse secant, depending on the choice of range made in the definition of the inverse secant function).