Chua Yi Cheng's answer to serendipity's Secondary 4 A Maths Singapore question.
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use the formula where cos(a+b) = cos(a)cos(b) - sin(a)sin(b) and cos(a-b) = cos(a)cos(b) + sin(a)sin(b) to expand out the fraction. i hope you understand!
Date Posted:
2 years ago
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