Given angle A and two sides, find Angle B.

[JacklinH.]

Homework Statement

In triangle ABC, A=65 degrees, b=9, and a=10. Find B.

Homework Equations

The Attempt at a Solution

I honestly don't know how to start this problem... I tried to use the law of cosines to find side C, and then again to find Angle B, but that answer was incorrect. I haven't been in Trig for two years, and can't think of how else to start it.

Thanks for any help!

 

[Bohrok]

Try the law of sines.

 

[Дьявол]

First use the sine to find h, and then use again the sine to find B, using arcsin(B).

$$\sin A = \frac{h}{b}\text{ and } \sin B = \frac{h}{a}.$$

Regards.

 

[HallsofIvy]

First use the law of sine to find h, and then use again the law of sine to find B, using arcsin(B).

$$\sin A = \frac{h}{b}\text{ and } \sin B = \frac{h}{a}.$$

Regards.

so that h= b sin A= a sin B and, as a result, $\frac{sin A}{a}= \frac{sin B}{b}$. That is the "sine law" Bohrok is talking about.

 

[Дьявол]

so that h= b sin A= a sin B and, as a result, [math]\frac{sin A}{a}= \frac{sin B}{b}[/math]. That is the "sine law" Bohrok is talking about.

Yes, you're right. I misspelled the words. I thought of "sine" and not "sine law".

Anyway, the things are same, and he would come up with the same result.

 

[HallsofIvy]

Yes, I wasn't criticizing, just pointing out to JacklinH that you were both giving the same advice!