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secondary 3 | A Maths
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can someone help me with this question , thank you!!
sin(3A)
= sin(A+2A)
= sinAcos2A + cosAsin2A
= sinA(1-2sin²A) + 2sinAcos²A
= sinA(1-2sin²A) + 2sinA(1-sin²A)
= 3sinA - 4sin³A
sin2x = 2sin x • cos x
(cos x - sin x)²
= cos² x + sin² x - 2sin x • cos x
= 1 - 2sin x • cos x
= 1 - sin2x
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