lesterine's answer to Danial's Secondary 3 A Maths Singapore question.
done
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I'm a little rusty at this but I hope it's accurate and helpful
Date Posted:
2 years ago
Got to take the negative value for cos x/2 because a third-quadrant angle x (180 < x < 270) implies that angle x/2 is a second-quadrant angle (90 < x/2 < 135) so it’s cosine is negative
ah okay thanks!!
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