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The Pythagorean Theorem
 Objectives: To find the length of one side of a right triangle, given the lengths of the other two sides, and to determine whether a triangle is right, given the lengths of its three sides.

  The Pythagorean Theorem: If triangle ABC is a right triangle with c the length of the hypotenuse and a and b the lengths of the legs, then c2 = a2 + b2

The Greek philosopher Pythagoras discovered the relationship between the hypotenuse and the two legs of a right triangle. right triangle is any triangle with one right angle.

  Converse of the Pythagorean Theorem: If c2 = a2 + b2, where a, b, and c are lengths of a triangle, then triangle ABC is a right triangle.

Examples: a.) A surveyor walked 8m east then 6m north. How far is she from the starting point?


Use the Pythagorean Theorem:
c2 = a2 + b2
= 62 + 82
= 36 + 64
= 100 c2 = 10 (the square root of 100)
Thus, the surveyor was 10m from her starting point.

b.) Determine whether the triangle with sides 3, 1, and is a right triangle:
c2 = a2 + b2
32 = 32 + 12
9 = 9 + 1
True; the triangle is right.