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secondary 4 | A Maths
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girl
Girl

secondary 4 chevron_right A Maths chevron_right Singapore

How do you do (ii)? This looks like r formulae but I’m not sure how to go about with finding the constants

Date Posted: 3 years ago
Views: 244
Eric Nicholas K
Eric Nicholas K
3 years ago
Girl, we bring the sin x over to the other side.

4 cos x - 3 sin x = 2

For the LHS,

R
= sqrt (4^2 + 3^2)
= 5

Phase shift alpha
= taninv (3/4)
= 0.6435011088 rad
~ 0.644 rad

So, the LHS becomes 5 cos (x + 0.644).

The equation becomes 5 cos (x + 0.644) = 2.
girl
Girl
3 years ago
Oh I get it now, I just didn’t divide 2/5 to get 0.4. Thank you!!
Eric Nicholas K
Eric Nicholas K
3 years ago
The equation solving requires the division of 5 first so that the LHS will be a cosine-only expression without the coefficient 5. Then, you should be able to solve the equation from there. Let me know if you also need help for the equation solving partz
girl
Girl
3 years ago
Okay I’ll try it out after I eat
girl
Girl
3 years ago
yeaaah I got it

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