Cosine Law: Query About Equation | Online Physics Course

[paolostinz]

My online physics course is using cosine law to find the net forces on objects. My question is to do with the equation, at first it shows it as : c^2=a^2+b^2-2ab cosC.

From there, it changes to: c=[a^2+b^2-2ab cosC]^1/2.

How and why does this work? Why isn't a square root involved in the operation?

 

[R136a1]

The notation ##x^{1/2}## is just another notation for ##\sqrt{x}##. Was that your question?

 

[paolostinz]

Yes, thank you! I see now, it seemed like I was getting the wrong answer when I was doing the original equation, so I thought something else was at play here.

Is there any reason why one would prefer writing the equation this way? I just don't get why my textbook would switch the equation when trying ton present new information.

 

[tiny-tim]

hi paolostinz!

Is there any reason why one would prefer writing the equation this way? I just don't get why my textbook would switch the equation when trying ton present new information.

you mean, writing c instead of c² ?

or writing (…)^1/2 instead of √(…) ?

we usually want c itself, so the fact that it comes from an equation with c² is a nuisance

(…)ⁿ is the general way of writing powers: there's no really good reason for having a special symbol when n = 1/2, and the bar of √, which should really go over the top of the bracket, is a nuisance when the bracket is long

 

[paolostinz]

See, that makes sense, it's the little things like this that confuse me most. I wish I had better access to teachers to clear up these type of hiccups. I'm so grateful for this place, thank you everyone!