# Help With The Law of Sines

Gold Member

## Homework Statement

Find a by using The Law of Sines by knowing that c=12, angle A=42o, angle C=69o.

## Homework Equations

(sin A)/a=(sin B)/b=(sin C)/c

## The Attempt at a Solution

I tried putting it in, but all I got was this correct, but useless equation:
6511/7990=383/470
I did it 1 more time, but still it wasn't successful.

I am not sure how you go the numbers you did in the solution attempt. The sine of the angles will give you numbers less than 1. I get the answer 8.6 for a

MathWA
Gold Member
Well, I did a lot of factoring with decimals, so I must had got them mixed up.
By the way calculators are allowed.

Gold Member
The answer is actually 9.34, but I need the solution(step-by-step work).

Gold Member
I am not sure how you go the numbers you did in the solution attempt. The sine of the angles will give you numbers less than 1. I get the answer 8.6 for a

I recalculated and got 61, instead, but its wrong!

Gold Member
Well, I got c equals to 50.

Can you write out line by line what you are doing, please?

Gold Member
Can you write out line by line what you are doing, please?
That would take a while, but sure, but not now(I'm very busy)
I can give you the last couple of lines:
(0.94)/a=47/ac
c=50
0.94/a=0.77/50
47=0.77a

well, firstly if 0.94 is your answer to sin42, that isn't right. I get something closer in radian mode.

Gold Member
Oops, I typed the wrong problem!
c is 12, angle A is 110, and angle C is 50

That would take a while, but sure, but not now(I'm very busy)
I can give you the last couple of lines:
(0.94)/a=47/ac
c=50
0.94/a=0.77/50
47=0.77a

So, is this work using the new values then? where did 47 come from?

$$\frac{a}{sin110}=\frac{12}{sin50}$$

This is how I would start it. THen I would use algebra to solve for the unknown.

Gold Member
I figured the problem out! Thank you, rpthomps!

Gold Member
I made the problem too confusing!

Mark44
Mentor

## The Attempt at a Solution

I tried putting it in, but all I got was this correct, but useless equation:
6511/7990=383/470
Yes, this is useless. Since you're trying to solve for a, your equation here should have a in it somewhere.
The answer is actually 9.34, but I need the solution(step-by-step work).
That's not how it works here. We'll help you get to a solution, but we aren't going to give it to you step by step.