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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.

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.

Date Posted:
2 months ago

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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. :)

Date Posted:
2 months ago

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Here's how I got the trigo function (a reference of an another student's qn).

Date Posted:
2 months ago