Write down the Java expression for: square root of (a^2 + b^2 + c^2)

Math.sqrt(a * a + b * b + c * c)

Everything under the radical becomes the single argument of Math.sqrt(), so all three squared terms go inside one pair of brackets. Write the squares as a * a rather than Math.pow(a, 2) — shorter, and it avoids the double return type of pow(). The commonest error is bracketing only part of the expression: Math.sqrt(a * a) + b * b + c * c would take the root of a squared alone. Whenever a radical spans several terms, that span is one pair of brackets.