The equation for the area of a tirangle is 

The base in this equation is  and the height is  which can be plugged into the formula as:



Finally, we multiply to get:

The key to solving this problem is remembering what an equilateral triangle is.  In case you forgot, a quick word breakdown will help.  It's easy to see that the first part of the word, "equi" looks an awful lot like equal.  The second part, "lateral", is a little trickier, but we only need to remember that lateral means "side".  In football, a lateral pass is when the player with the ball tosses it to a player on either side.  Putting the two parts together, we see that equilateral just means equal sides.  Therefore an equilateral triangle is a triangle where all three sides have equal length.  That means that if one side of our equilateral triangle has length of , the other two sides are also each  long.

We must also remember that the perimeter of a shape is just the distance around the outside of it.  For our triangle, that means  for the first side,  for the second side, and  for the third side.  That means our perimeter is simply .

To begin, first find the length of the third side of the triangle. We are given that the two short sides of the triangle have lengths of 5 and 12. Use the Pythagorean Theorem to find the length of the third side:

,

where  and  represent the two shorter sides of the triangle, and  is the hypotenuse:

Now that we have the lengths of all three sides, add them together to find the perimeter:

The perimeter of the triangle is 30.

The correct answer to the question is .

The formula for finding the perimeter of a triangle is to find the sum of the length of the  sides. 

The lengths of the three sides of this triangle are , , and . If you add these  sides, the sum is a perimeter of .

Using the Pythagorean Theorem, the length of the second leg can be determined.

We are given the length of the hypotenuse and one leg.

The perimeter of the triangle is the sum of the lengths of the sides.

The perimeter of a shape is the length around the shape. In order to find the perimeter of a triangle, add the lengths of the sides: .

Because the lengths are in inches, the answer must be in inches as well.

Equilateral triangles have  sides of equal length. Therefore, by knowing the length of one side, we can calculate the perimeter by multiplying that length by . 

Because the triangle is equilateral, all sidelengths are equal. Thus, if one is 8 they all must be 8, so 

In an isosceles triangle, two of the three sides are equal to each other.  The possible side lengths of the isosceles are  or .

The perimeter is the sum of the three sides.

The only possible perimeters given the two side lengths are either  or .

The correct answer is:  

There are three equal sides in an equilateral triangle.  

Substitute the side length.