Find angle theta in the second quadrant if sin theta = 1/2

Answer 1

sin^-1 0.5 = 30°

In QII, that is 150°

Answer 2

SIN(θ) = 1/2 implies that SIN^-1(1/2) = θ. Because that's what inverse functions do.

However, inverse trig functions are SKETCHY. They can only give answers in certain quadrants.

Make sure your answer is in the right quadrant. You may need to reflect it into another quadrant.

Type SIN^-1(1/2) into your calculator (the inverse SIN is often SHIFT + SIN or 2ND + SIN on the calculator).

You'll get 30° if your calculator is in degree mode or π/6 (≈.5236) if you're in radian mode.

That's in the 1st quadrant. Dang.

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