2 Solve the equation \(\sec ^ { 2 } \theta \cot \theta = 8\) for \(0 < \theta < \pi\).
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Question 2:
Answer Marks
Guidance
Answer Marks
Guidance
State \(\frac{1}{\cos^2\theta} \times \frac{\cos\theta}{\sin\theta} = 8\) B1
OE involving \(\sin\theta\) and \(\cos\theta\) only
Attempt use of \(\sin 2\theta\) identity to obtain \(\sin 2\theta = k\) M1
Obtain \(\sin 2\theta = \frac{1}{4}\) A1
Use correct process to find two values of \(\theta\) between 0 and \(\pi\) M1
Allow if working in degrees
Obtain 0.126 and 1.44 A1
AWRT
Alternative: State \(\frac{1+\tan^2\theta}{\tan\theta} = 8\)B1
Attempt solution of 3-term quadratic equation to find values of \(\tan\theta\) M1
OE involving \(\tan\theta\) only
Obtain \(\tan\theta = \frac{8 \pm \sqrt{60}}{2}\) A1
OE
Solve \(\tan\theta = \ldots\) to find two values of \(\theta\) between 0 and \(\pi\) M1
Allow if working in degrees
Obtain 0.126 and 1.44 A1
AWRT
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## Question 2:
| Answer | Marks | Guidance |
|--------|-------|----------|
| State $\frac{1}{\cos^2\theta} \times \frac{\cos\theta}{\sin\theta} = 8$ | B1 | OE involving $\sin\theta$ and $\cos\theta$ only |
| Attempt use of $\sin 2\theta$ identity to obtain $\sin 2\theta = k$ | M1 | |
| Obtain $\sin 2\theta = \frac{1}{4}$ | A1 | |
| Use correct process to find two values of $\theta$ between 0 and $\pi$ | M1 | Allow if working in degrees |
| Obtain 0.126 and 1.44 | A1 | AWRT |
| **Alternative:** State $\frac{1+\tan^2\theta}{\tan\theta} = 8$ | B1 | |
| Attempt solution of 3-term quadratic equation to find values of $\tan\theta$ | M1 | OE involving $\tan\theta$ only |
| Obtain $\tan\theta = \frac{8 \pm \sqrt{60}}{2}$ | A1 | OE |
| Solve $\tan\theta = \ldots$ to find two values of $\theta$ between 0 and $\pi$ | M1 | Allow if working in degrees |
| Obtain 0.126 and 1.44 | A1 | AWRT |
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2 Solve the equation $\sec ^ { 2 } \theta \cot \theta = 8$ for $0 < \theta < \pi$.\\
\hfill \mbox{\textit{CAIE P2 2021 Q2 [5]}}