The answer depends on what the shape is: triangle, quadrilateral or one with many more sides. You do need to specify these things in the question because, unfortunately, we have not mastered the art of reading your mind over the web.
One way to find a missing side length of a triangle is to use the Pythagorean theorem, which states that in a right triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the other two sides (a² + b² = c²). If you know the lengths of two sides, you can rearrange the formula to solve for the missing side. For example, if you have the lengths of the two legs (a and b), you can find the hypotenuse (c) by calculating c = √(a² + b²).
you must know more information. Like the lengths of 2 sides. Then using Trig (law of sines or law of cosines) you can find the remaining sides and angles.
The answer depends on what the problem is: are you required to find the lengths of the missing sides, the area, angles, length of diagonal, or WHAT!
Add together the lengths of the four sides; or add the lengths of the two different sides and then double it.
That really depends what else you know about the triangle. For example, if you only know the lengths of two sides, you simply don't have enough information.
One way to find a missing side length of a triangle is to use the Pythagorean theorem, which states that in a right triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the other two sides (a² + b² = c²). If you know the lengths of two sides, you can rearrange the formula to solve for the missing side. For example, if you have the lengths of the two legs (a and b), you can find the hypotenuse (c) by calculating c = √(a² + b²).
you must know more information. Like the lengths of 2 sides. Then using Trig (law of sines or law of cosines) you can find the remaining sides and angles.
Surely you know how to find the third side of a right triangle, when you know the lengths of the other two. Find it, and then add up the lengths of the three sides to get the perimeter.
The answer depends on what the problem is: are you required to find the lengths of the missing sides, the area, angles, length of diagonal, or WHAT!
In order to find the perimeter of a 3D rectangle you must gather the lengths of the known sides, calculate the missing rectangular values, and use the formula for perimeter.
Add together the lengths of the four sides; or add the lengths of the two different sides and then double it.
That really depends what else you know about the triangle. For example, if you only know the lengths of two sides, you simply don't have enough information.
It depends on which side is missing. If the hypotenuse (longest side, opposite right angle) is missing, square the lengths of the other two sides, add them, and then square root your answer. If a leg is missing, square the two remaining sides, subtract the smaller from the larger, and square root it. All of this is derived from the Pythagorean Theorem: a^2+b^2=c^2, where a and b are the lengths of the two legs and c is the length of the hypotenuse.
Find the perimeter by adding the lengths of the sides
If you know the lengths of two sides then use Pythagoras' theorem to find the third side.
You add the lengths of all the sides. If the sides happen to be of equal length, you multiply this length by 7.
Add the lengths of the four sides