Help With The Law of Sines

  • #1
MathWA
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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. :frown:
Please Help!
 

Answers and Replies

  • #2
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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
 
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  • #3
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Well, I did a lot of factoring with decimals, so I must had got them mixed up.
By the way calculators are allowed.
 
  • #4
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The answer is actually 9.34, but I need the solution(step-by-step work).
 
  • #5
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Show me your work.
 
  • #6
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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!
 
  • #7
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Well, I got c equals to 50.
 
  • #8
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Can you write out line by line what you are doing, please?
 
  • #9
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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
a is about 61
 
  • #10
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well, firstly if 0.94 is your answer to sin42, that isn't right. I get something closer in radian mode.
 
  • #11
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Oops, I typed the wrong problem!
c is 12, angle A is 110, and angle C is 50
Sorry about that rpthomps!
 
  • #12
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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
a is about 61
So, is this work using the new values then? where did 47 come from?
 
  • #13
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$$\frac{a}{sin110}=\frac{12}{sin50}$$

This is how I would start it. THen I would use algebra to solve for the unknown.
 
  • #14
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I figured the problem out! Thank you, rpthomps!:smile::smile::smile:
 
  • #15
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I made the problem too confusing!
 
  • #16
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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.

Start with what rpthomps write in post #13.
 
  • #17
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I figured the problem out! Thank you, rpthomps!:smile::smile::smile:
You're welcome
 

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