# Algebra/ Trig question

#### EasyEngineer

I just need to know how to solve for alpha. If some context helps, it's to calculate the firing angle of an AC to AC converter. I just need to know how they went from 2a - sin(2a) = 3pi/2 to 1.98665 rads.

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#### skeeter

Math Team
Given the decimal solution, they most probably used technology. I don't believe an elementary algebraic solution is possible.

Graphed the following equation and solved for its roots(s) shown in the attached

$2\alpha -\sin(2\alpha) - \dfrac{3\pi}{2} = 0$

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#### EasyEngineer

Ok when I use Wolfram this is exactly what they got. I thought there would be a way to solve for alpha by moving the sin over or something. Thank you for your time.

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