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2 years ago

I need help with this question pleas e

Mathematics

1 answer:

ollegr [7]2 years ago

4 0

Answer:

Step-by-step explanation:

The double angle formulae for cosine is

cos2x = cos²x - sin²x

[ using sin²x + cos²x = 1 ]

cos2x = cos²x - (1 - cos²x) = cos²x - 1 + cos²x = 2cos²x - 1

Also cos2x = (1 - sin²x) - sin²x = 1 - sin²x - sin²x = 1 - 2sin²x

The double angle formulae are

cos2x = cos²x - sin²x = 2cos² - 1 = 1 - 2sin²x

Hence

cos60° = cos²30° - sin²30°

cos60° = 2cos²30° - 1

cos60° = 1 - 2sin²30°

B is not a representation of cos60°

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