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secondary 3 | A Maths
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lana <3
Lana <3

secondary 3 chevron_right A Maths chevron_right Singapore

someone pls me with this

Date Posted: 2 years ago
Views: 240

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Ashley Yeo Sze Lin
Ashley Yeo Sze Lin's answer
3 answers (Tutor Details)
1st
For part 1, use the trigo identities to derive the answer
For part 2, sub in the answer from part one and do not divide, as the solution will not make sense (you would get 1 = sqrt(2))
lana <3
Lana <3
2 years ago
hi! how to you get theta - 70 = 90 or 270 ?? how do yk its 90 or 270
Ashley Yeo Sze Lin
Ashley Yeo Sze Lin
2 years ago
so to get a solution, cos (theta - 70) must be zero. only cos 90 and cos 270 are equal to 0 in the given range
lana <3
Lana <3
2 years ago
oh I think I understand! so if sin(theta+20) = 0 the range would be 180 < theta < 360
Ashley Yeo Sze Lin
Ashley Yeo Sze Lin
2 years ago
so the way i understood the concept was that the cos value corresponds to the x value of the angle drawn. since theta is between 0 and 360, theta -70 is between -70 and 290. i used cos for this qtn