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Solve, for $0 \leq \theta \leq 180^{\circ}$, $$2\cot^2(30^{\circ}) = 7\csc(30^{\circ}) - 5$$ Give your answers in degrees to 1 decimal place. - Edexcel - A-Level Maths Pure - Question 7 - 2012 - Paper 6

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Question 7

Solve,-for-$0-\leq-\theta-\leq-180^{\circ}$,--$$2\cot^2(30^{\circ})-=-7\csc(30^{\circ})---5$$--Give-your-answers-in-degrees-to-1-decimal-place.-Edexcel-A-Level Maths Pure-Question 7-2012-Paper 6.png

Solve, for $0 \leq \theta \leq 180^{\circ}$, $$2\cot^2(30^{\circ}) = 7\csc(30^{\circ}) - 5$$ Give your answers in degrees to 1 decimal place.

Worked Solution & Example Answer:Solve, for $0 \leq \theta \leq 180^{\circ}$, $$2\cot^2(30^{\circ}) = 7\csc(30^{\circ}) - 5$$ Give your answers in degrees to 1 decimal place. - Edexcel - A-Level Maths Pure - Question 7 - 2012 - Paper 6

Step 1

Rewrite the equation with known values

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Answer

Since heta=30 heta = 30^{\circ}, we know that cot(30)=13 and csc(30)=2 \cot(30^{\circ}) = \frac{1}{\sqrt{3}} \text{ and }\csc(30^{\circ}) = 2 . We can substitute these values into the equation:

2(13)2=7(2)5.2\left(\frac{1}{\sqrt{3}}\right)^2 = 7(2) - 5.

Step 2

Simplify the equation

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Answer

Now, simplifying both sides:

23=145\frac{2}{3} = 14 - 5

This leads to:
23=9,\frac{2}{3} = 9, which is incorrect, indicating that we should derive solution for heta heta.

Step 3

Set up the equation cos(θ)

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Answer

We can reorder and form an equation:

2cot2(θ)=7csc(θ)52\cot^2(\theta) = 7\csc(\theta) - 5

Substituting again: 2cot2(θ)=145=92\cot^2(\theta) = 14 - 5 = 9 This will yield to finding heta heta.

Step 4

Solve for θ

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Answer

After reorganizing, cot2(θ)=92\cot^2(\theta) = \frac{9}{2} This leads to θ=\arccot(32)\theta = \arccot\left(\frac{3}{\sqrt{2}}\right)
Calculate principal solution:

Using calculator, find: θ53.5.\theta \approx 53.5^{\circ}. Also, check the domain and the possible secondary solution: θ=18053.5126.5.\theta = 180^{\circ} - 53.5^{\circ} \approx 126.5^{\circ}.

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