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secondary 4 | A Maths
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Anonymous
Anonymous

secondary 4 chevron_right A Maths chevron_right Singapore

hi why is there a squareroot applied to -1+cos210/2?

Date Posted: 4 months ago
Views: 90
Eric Nicholas K
Eric Nicholas K
4 months ago
They forgot the “square” in one of the lines preceding that line
Anonymous
Anonymous
4 months ago
ohh I see. so what's the missing step supposed to look like?
Eric Nicholas K
Eric Nicholas K
4 months ago
As in, after the line “2A = 210”, it should be “cos^2 105 = …” rather than “cos 105 = …”.

We simply take square root after that; however, we take the negative version because cos 105 is the cosine of a second-quadrant angle and its value is expected to be negative.

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Arnold K H Tan
Arnold K H Tan's answer
1517 answers (A Helpful Person)
1st
Just a typo