# How do I find the value of sin 150?

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#### Explanation

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19
Nghi N. Share
Sep 16, 2015

Find sin 150

#### Explanation:

You may find sin 150 by 2 ways:

First way. Trig Table gives --> sin 150 deg, or $\sin \left(\frac{5 \pi}{6}\right)$, = 1/2
Second way: by the trig unit circle.

$\sin \left(\frac{5 \pi}{6}\right) = \sin \left(\frac{\pi}{6}\right) = \frac{1}{2}$

Then teach the underlying concepts
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#### Explanation

Explain in detail...

#### Explanation:

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4
Sep 14, 2015

Answer is 1/2: Draw a unit circle / memorize some formulas.

#### Explanation:

Well, on a unit circle these are the definitions of sine, cosine, and tangent values.

sine: y value
cosine: x value
tangent: y/x value

So if you draw a large arc corresponding to 150 degrees from the x axis, counterclockwise, you end up in the 2nd quadrant. Since 150's supplement is 30s, basic trig tells you that the y value for your point is 1/2...and there you go!

If you think this is inconvenient you can memorize formulas like sinx= sin(2pi-x) but well I don't really prefer it. Especially if you're talking about simple angles less than 180.

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