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secondary 4 | A Maths
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MM
MM

secondary 4 chevron_right A Maths chevron_right Singapore

Help to solve

Date Posted: 3 years ago
Views: 214

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Make all becomes 2X

Cosec(2X) =1/Sin(2X)

Cos(4X) = cos (2.2X) therefore.... using double angle formula

Then can solve for part (1)

Quadratic equation
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Kahwai
Kahwai's answer
232 answers (A Helpful Person)
1st
MM
MM
3 years ago
Need steps please
For part 2

0 0<2X<2Pi()

Then

Differentiate y
You get something with cot(2X)

Equate both
Left with sine(2x) and cosine (2x)

Then using (a2+b2)^0.5 sin(theta + alpha) formula or sine square plus cosine square =1

You will get the answers
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Kahwai
Kahwai's answer
232 answers (A Helpful Person)
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Kahwai
Kahwai's answer
232 answers (A Helpful Person)
I jumped many steps but you need to try it yourselves
MM
MM
3 years ago
Can't understood
Kahwai
Kahwai
3 years ago
You can’t understand?
Okay no problem

1. Take a deep breath and be grateful and patient

2. Read the question, what do you observe?
A. Cos4X, and the rest are sin(2x), cosec(2x) is 1/sin(2x)
B. Change cos 4x to cos2x, how? By 1+cos2theta = cos^2(theta)
Got it?
C. You have cos^(2x) what do you do?
Change it to
Sin^2(2x), got it
D. Factorize
E. |Sin2X|<1, then cancellation
F. Partial faction
G. QED

Part 2.
A. Change all to sine and cosine
B, differentiate ( refer to your text book)
C. Equate two equations
D. Get cos2x as -1, then solve

You need to practise and read text book, if not discuss with your friends and practise more. And you cannot hate it because without practise and knowing the formulae you can’t understand





M
Kahwai
Kahwai
3 years ago
Once you practise and undetabd how to do this sum you can undetabd most of the trigometry and derivative problems .

Learn with the right attitude you can do it!