Equations with equal cosines and with a double-angle sine equal to a cosine
Equations with equal cosines and with a double-angle sine equal to a cosine
IB Year 6 | Grade 12
10 marks
- Solve the equation \(\cos4x=\cos x\) for \(0\le x\le\pi\).[4]
- Solve the equation \(\sin4x=\cos2x\) for \(0\le x\le\pi\).[6]
Solution:
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Answer:(a) \(x=0,\ \frac{2\pi}5,\ \frac{2\pi}3,\ \frac{4\pi}5\) (b) \(x=\frac\pi{12},\ \frac\pi4,\ \frac{5\pi}{12},\ \frac{3\pi}4\)
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