How do you evaluate $sin^-1(-1/2)$ without a calculator?

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Answer 1 · 2016-12-05T11:05:50

The answer is $S={210º,330º}$

We know that $sin30º=1/2$

So, we are looking for a solution in the 3rd and 4th quadrant

$sintheta=-1/2$

$theta=210º$ and $theta=330º$

if $0< theta<= 360$

How do you evaluate sin^-1(-1/2)sin^-1(-1/2) without a calculator?