Math CentralQuandaries & Queries


Question from Xanathax, a student:

ABC is a right-angled triangle. 2sinB=3tanA.
Calculate the measure of angle A.


Since A and B are the two non-right angles in a right triangle you know that B = 90o - A. Hence your equation can be written

2 sin(90o - A) = 3 tanA

Expand the left side using the multiple angle formula for the sine function. Evaluare sin(90o) and cos(90o) and solve the resulting equation for A.


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