For a right triangle, a² + b² = c², where a and b are the legs and c is the hypotenuse. The hypotenuse is opposite the 90° angle and is the longest side.
To find the hypotenuse, square both legs, add, then take the square root.
Example: legs 6 cm and 8 cm give c² = 6² + 8² = 36 + 64 = 100, so c = √100 = 10 cm.
To find a missing leg, subtract: if c = 13 and a = 5, then b² = 13² − 5² = 169 − 25 = 144, so b = 12.
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