2020 ONE(b)

Achievement
Question
Find the gradient of the tangent to the curve y=3sin2x+cos2xy = 3\sin 2x + \cos 2x at the point where x=π4x = \dfrac{\pi}{4}.

*You must use calculus and show any derivatives that you need to find when solving this
problem.*
Official Answer
y=3sin2x+cos2xy=3\sin 2x+\cos 2x
dydx=6cos2x2sin2x\dfrac{dy}{dx}=6\cos 2x-2\sin 2x

At x=π4x=\dfrac{\pi}{4}, dydx=6cosπ22sinπ2=2\dfrac{dy}{dx}=6\cos \dfrac{\pi}{2}-2\sin \dfrac{\pi}{2}=-2
Grading Criteria

Achievement (u)

  • Correct gradient with correct derivative.

Merit (r)

-

Excellence T1

-

Excellence T2

-
Video Explanation
NCEA Level 3 Calculus Differentiation 2020 NZQA Exam - Worked Answers by infinityplusone(starts at 1:39)
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