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secondary 4 | A Maths
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Ong Jia Zhi
Ong Jia Zhi

secondary 4 chevron_right A Maths chevron_right Singapore

How to do 7 part 3?

Date Posted: 5 months ago
Views: 24

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Eric Nicholas K
Eric Nicholas K's answer
2980 answers (Tutor Details)
1st
In part (i), because angle 2A is twice that of angle A, you use the double angle formula right?

In part (iii), angle A is twice that of angle 0.5A, so the double angle formula applies here as well.

Note, however, the quadrant which 0.5A lies in. Since A lies from 180 to 270, it follows that 0.5A lies from 90 to 135, which is somewhere in the second quadrant. As a result, tan 0.5A will emerge as a negative value.

We just pluck in the value of tan A into the double angle formula for the angle A and angle 0.5A pair of angles and then form a quadratic-like equation for tan 0.5A and solve for it.
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Mathaddict100
Mathaddict100's answer
348 answers (A Helpful Person)
This is another way you can change Tan(1/2)A to SinA/(CosA+1)..After that,you just need to substitute the values of SinA and CosA to the new trigo function formed.Try memorising this formula for the half angle of tan so as it will be easy for you..Hope this helps. :)
Mathaddict100
Mathaddict100
5 months ago
*newly*
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Mathaddict100
Mathaddict100's answer
348 answers (A Helpful Person)
Here's how I got the trigo function (a reference of an another student's qn).