Please help me do 9c fast please
1 answer:
Answer:
see explanation
Step-by-step explanation:
Using double angle formulae for cosine and sine
Consider left side
cos4θ
= cos2(2θ)
= cos²(2θ) - sin²(2θ)
= [ cos²θ - sin²θ ]² - (2sinθcosθ)²
= [ (1 - sin²θ - sin²θ ]² - (2sinθcosθ)²
= (1 - 2sin²θ )² - (2sinθcosθ)²
= 1 + 4θ - 4sin²θ - 4sin²θcos²θ
= 1 + 4θ - 4sin²θ - 4(1 - sin²θ)sin²θ
= 1 + 4θ - 4sin²θ - 4sin²θ + 4
θ
= 1 - 8sin²θ + 8θ
= right side , thus proven
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Explanation:
This question's it's about the order of operations. P-parenthesis, E-exponents, M-multiply, D-divide, A-add, and S-subtract. It can also go left to right.
Do exponents first.
Then, multiply left to right.
And add/subtract left to right.
Hope this helps!
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