Question 6

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Jambmaths question: 

Differentiate ${{(\cos \theta -\sin \theta )}^{2}}$ with respect to θ

Option A: 

$-2\sin 2\theta$

Option B: 

$-2\cos 2\theta$

Option C: 

$1-2\cos 2\theta$

Option D: 

$1-2\sin 2\theta$

Jamb Maths Solution: 

$\begin{align}  & y={{(\cos \theta -\sin \theta )}^{2}}=(\cos \theta -\sin \theta )(\cos \theta -\sin \theta ) \\ & y={{\cos }^{2}}\theta +{{\sin }^{2}}-2\sin \theta \cos \theta  \\ & y=1-2\sin \theta \cos \theta  \\ & y=1-\sin 2\theta \text{                }\left| note:\sin 2\theta =2\sin \theta \cos \theta  \right. \\ & \frac{dy}{d\theta }=-2\cos 2\theta  \\\end{align}$

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