Triple angle identity via complex numbers
Triple angle identity via complex numbers
IB Year 6 | Grade 12
- Use complex number methods to show that \(\cos 3\theta = 4\cos^3\theta - 3\cos\theta\).
- Hence find the exact value of \(\cos^3\dfrac{5\pi}{12}\).
Solution:
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Answer:(a) Shown; \(\cos3\theta=4\cos^3\theta-3\cos\theta\) (b) \(\dfrac{3\sqrt6-5\sqrt2}{16}\)
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