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Lesson: Geometry - 19t01

Finding The Perimeter Of A Triangle

[Page 19 of 30]

What is the perimeter of the isosceles triangle in the diagram below? Choose an answer, and then click Continue.

4√2
6√2
12
8 + 4 √2
14

Countinue

The largest angle in a right triangle is always the right angle. This makes sense if we remember that the sum of the other two angles is 180° - 90° = 90°. This is an isosceles triangle, the other two angles must be equal, and each must be 45°.

Since sides are proportional to the angles that are opposite them, then the two legs of the triangle must be of equal length. We know that one leg is 4, so the other leg must also be 4.

Plug these numbers into the Pythagorean theorem to find the length of the hypotenuse:

Then add the sides to find the perimeter:

4 + 4 + 4√2 = 8 + 4√2

Next to display next topic in the chapter.

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