Eric Nicholas K's answer to Ong Jia Zhi's Secondary 4 A Maths Singapore question.
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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:
5 years ago