# Mathbook problem - Geometry

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I got this problem and im not going to meet the teacher untill next monday and i want to progress further so maby you can help me?
The question is:

What are the angels of the triangle ABC if
A = 2B
B < 45 degres
SinC = 0.5

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sin C = 0.5, meaning C is 30 degrees, therefore we have 150 degrees left for the other 2 angles.

A = 2B
A + B = 150
Wolfram solves it with result of A = 100, B = 50 (the only solution)
However you said B < 45, meaning it cannot be solved or you wrote/read something incorrectly.

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sin C = 0.5 means either C is 30 degrees, or C is 150 degrees. Ripiz just explained why it can't be 30 degrees, therefore it's 150 degrees, A is 20 degrees and B is 10 degrees.

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I also got C = 30, thats what the calc says. How do you know it can also be 150?

Thanks

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I also got C = 30, thats what the calc says. How do you know it can also be 150?

I don't know... A decent high school education?

What do you know about the sine function? The way I think about it, it's the height of a point in the trigonometric circle. It should be fairly obvious then that sin(x) = sin(180 degrees - x).

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Ripiz just explained why it can't be 30 degrees, therefore it's 150 degrees

Damn that's right... I completely forgot about the other half. Sorry for my mistake and thanks for pointing out.

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Yes thank you for you help.

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