The **Pythagorean Theorem** is a fundamental principle in geometry that relates the lengths of the sides of a right-angled triangle. It states: > **In a right-angled triangle, the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides (legs).** ### Formula: \[ \boxed{a^2 + b^2 = c^2} \] Where: - \( c \) = hypotenuse (longest side) - \( a \) and \( b \) = other two sides (legs) ### Example: If a right triangle has legs of lengths \( 3 \) and \( 4 \), the hypotenuse \( c \) is calculated as: \[ 3^2 + 4^2 = c^2 \\ 9 + 16 = c^2 \\ 25 = c^2 \\ c = \sqrt{25} = 5 \] This theorem is named after the ancient Greek mathematician **Pythagoras**, though it was known to Babylonians and Indians earlier. It has wide applications in mathematics, physics, engineering, and more.

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