Solve for Angle A: Law of Sines Problem"

[bengaltiger14]

Law of sines Problem...

Homework Statement

Solve for angle A:

sin(135)/56.6 = sin(A)/45 = sin(15)/15

The Attempt at a Solution

sin(135)/56.6 = sin(A) = 45sin(15)/15

Am I on the correct track?

 

[G01]

You are on the right track, and you have the right idea, but you seem to be confused with that second equal sign.

$$\frac{\sin 135}{56.6}=\frac{\sin A}{45}=\frac{\sin 15}{15}$$

All this above line says is:

$$\frac{\sin A}{45}= \frac{\sin 15}{15}$$

and

$$\frac{\sin A}{45}=\frac{\sin 135}{56.6}$$All you have to do is pick one of the above equations. They should give you the same answer. Does this help?

 

[bengaltiger14]

it sure does... I was trying to solve all together at once. Could not figure out how but that makes sense what you said. Thanks.

 

[G01]

No Problem!

 

[Dick]

Homework Statement

Solve for angle A:

sin(135)/56.6 = sin(A)/45 = sin(15)/15

The Attempt at a Solution

sin(135)/56.6 = sin(A) = 45sin(15)/15

Am I on the correct track?

I'm confused. Why not just use 135+A+15=180 to solve for A? And with the given figures all of the ratios are only roughly equal. Are we really solving the correct problem?

 

[mgb_phys]

I suspect we are too clever for our own good!

 

[HallsofIvy]

This is the second question I have seen posted under "physics" that had no physics in it! Why isn't this posted under a mathematics thread?

 

[mgb_phys]

Because us mere physicists are scared of going over there?

 

[Leong]

The question didn't mention that all the angles refer to the actual angles in the triangle. if the question says sin (165)/15. the below method will not work but the above method will work. right?

135+A+15=180

 

[Leong]

if it is not in the right place, why don't the moderator move it?

 

[Dick]

The question didn't mention that all the angles refer to the actual angles in the triangle. if the question says sin (165)/15. the below method will not work but the above method will work. right?

135+A+15=180

If the angles aren't the 'actual angles' of a triangle then what might they be and what could the law of sines have to do with them?

 

[Leong]

we must analyze based on what we have

 

[Dick]

we must analyze based on what we have

I give up.

 

[Leong]

in case you don't, i will...

 

[mgb_phys]

The law of sines only works for the internal angles of a triangle in a flat plane.
I checked in case it was a trick question about spherical trig.

 

[lugita15]

If the angles aren't the 'actual angles' of a triangle then what might they be and what could the law of sines have to do with them?

They can't be actual angles. They don't satisfy the triangle inequality.

 

[rocomath]

i been reviewing Trig and i still have yet to finish a chapter that I've been on for 3 days! i didn't think Trig would take this much work.

 

[Dick]

They can't be actual angles. They don't satisfy the triangle inequality.

Then what are they? This is silly. The OP gives more information than you actually need to solve the triangle and that extra information is inconsistant. You can pick three of the given sides or angles and solve a triangle - but you get somewhat different triangles depending on which three you pick.