# Thread: Missing parts of triangle

1. ## Missing parts of triangle help

How in the world do I find the missing parts of the triangle ABC if a = 12, b = 19, and A = 82 deg's?

Thanks very much

2. ## Law of sines

////a/
/.\
////a/\.\\b
a//./____\
.........
c

a = 12, b = 19, and A (opposite a) = 82 deg's

remember that $\frac{a}{sinA}=\frac{b}{sinB}=\frac{c}{sinC}$

now you can easily solve for B.

Once you have B you know that A+B+C = 180 so you can get C and finally use C and the law of sines to get c

let me know if you need more help

For angle B I get SinB = 19sin82deg / 12 which gives me 1.5679 and when I do arcsin 1.5679 I get an Error why is this?

4. ## Ambiguity in the stated question

The reason is that the problem is not clearly stated. There is no way that the angle opposite a is 82 degrees. It can only be between a and b (I would have called that angle C as it is opposite c) Try it again this way and you will get the answer.

5. I just realized Angle B could also be 82 degrees so you have to figure out which angle it is talking about.

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### how to find the missing part of a triangle videos

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