# Square Root Problem

• Dec 6th 2009, 05:38 PM
mjfaris
Square Root Problem
How do I solve Z=the square root of L^2 + R^2 for R.
• Dec 6th 2009, 05:44 PM
werepurple
I don't really know what you mean, but I'm guessing you want to make R the subject?

Hence, step by step,

=> Z = (L^2 + R^2)^(1/2)
=> Z^2 = L^2 + R^2
=> R^2 = Z^2 - L^2
=> R = (Z^2 - L^2)^(1/2) <======
• Dec 6th 2009, 08:16 PM
Noxide
Wouldn't it be:

=> R = +/- (Z^2 - L^2)^(1/2) <======

the +/- because you're solving for all values of R
• Dec 6th 2009, 08:19 PM
werepurple
Quote:

Originally Posted by Noxide
Wouldn't it be:

=> R = +/- (Z^2 - L^2)^(1/2) <======

the +/- because you're solving for all values of R

True, he didn't define the unknowns as positive values; this equation is very similar to the one I always use to solve physics questions; hence, I always disregard the - sign. lol, but thx for the correction!! I won't forget a lesson learnt.
• Dec 6th 2009, 08:23 PM
Noxide
actually that sparked a question...

when you are playing with variables in physics and you end up in a situation where x^(n/n) n is even do you put an absolute value symbol around x, or do you just remember that it's the positive case?
• Dec 6th 2009, 08:28 PM
werepurple
I don't play with variables in physics, and didn't end up in that situation you desribed. I use that formula to usually find the " change in velocity ", " " change in displacement ", and etc; in other words, I use that formula to solve simple problems most of the time, and it becomes a habit to simply take the positive value as the answer without considering the possible negative value, which is most of the time needless.