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Specialist Mathematics Β· Unit 2 Β· Trigonometry and functions Β· Trigonometric identities

Convert sums π‘Ž cos(π‘₯) + 𝑏 sin(π‘₯) to 𝑅 cos(π‘₯ Β± 𝛼) or 𝑅 sin(π‘₯ Β± 𝛼) and apply these to sketch graphs.

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Question 1

Consider the function \(f(x) = 5\cos(x) - 12\sin(x)\) where \(x \in \mathbb{R}\). (a) Convert \(f(x)\) into the form \(R\cos(x + \alpha)\), where \(R > 0\) and \(0 < \alpha < \frac{\pi}{2}\). Express \(R\) as an integer and \(\alpha\) in radians correct to 2 decimal places. (3 marks) (b) Hence determine the minimum value of \(f(x)\) and the smallest positive value of \(x\) at which this minimum occurs. Give \(x\) correct to 2 decimal places. (2 marks)

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Question 2

Convert the expression \(f(x) = 5\cos(x) - 12\sin(x)\) to the form \(R\cos(x + \alpha)\), where \(R > 0\) and \(0 < \alpha < 2\pi\).

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Question 3

Convert \(f(x) = 5\cos(x) - 12\sin(x)\) into the form \(R\cos(x + \alpha)\), where \(R > 0\) and \(0 < \alpha < \frac{\pi}{2}\). Express \(\alpha\) in radians correct to two decimal places.

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Model and solve problems that involve equations of the form π‘Ž cos(π‘₯) + 𝑏 sin(π‘₯) = 𝑐.
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