Measurement question?

Question

How do you figure out the diagnol length of a square when the sides of the square are undefined?

We know the square will be 30x30, but we dont know how many feet it is diagnally, thus we cant figure out how to square the other two sides. what is the formula?

I want to use the 3,4,5 rule, but since I am new noone will listen to me.

Answer 1

I'm not sure exactly what you are asking but if you have a 30x30 square and you want to find the length from one corner to another you simply use the Pythagorean theorem.

a^2 + b^2 = c^2 ...so...

30^2+30^2=C^2 =
900+900=C^2
1800=C^2
C=42.43 (square root of 1800)

(If you divide the square in half you have two triangles and can find the hypotenuse which is the diagonal part)

Answer 2

Think of the square and its diagonal as a triangle. Let's say the square has a side with length x. All sides must be x. Now, make a triangle by taking 2 sides and the diagonal. We can use Pythagreon's Theorem:

a^2 + b^2 = c^2

We have:

x^2 + x^2 = d^2
2x^2 = d^2
d = x*sqrt(2)

Answer 3

Another way to calc the diagonal, (not sure how familiar you are with trigonometry), but since it is a square, the angle of the diagonal is 45 degrees.

Sine (angle 45 deg) = opposite side (30 feet) / hypotenuse (diagonal)

diagonal = 30 feet / sine 45 deg = 42.426 feet.

Answer 4

since the real formula is a^2+b^2=c^2 and a-b in a square then 2a^2=c^2 so if a side is 30 then the formula is sqrt(2*30*30) or sqrt(1800) which is 42.43

Answer 5

Everyone above gave the correct formula -- one guy gave an numerical answer -- here it is in better terms:

42 feet, 5 1/8th inches (it's actually 5 1/6th of an inch, but...
If you can build your 30' x 30' structure to match both diagonals to within 1/2" you're doing very, very well.

.

Answer 6

since you're measuring a square, a 3-4-5 triangle does not apply.

if i understand your question properly, you need the pythagorean theorem, a^2 + b^2 = c^2, where c is your diagonal.