This question asks students to identify the formula for the space diagonal of a cuboid using 3D Pythagoras.
3D diagonal = √(length² + width² + height²).
To find the space diagonal of a cuboid with length l, width w, and height h, we treat it as a right-angled triangle in 3D. The diagonal forms the hypotenuse, and the three dimensions form the perpendicular sides. Apply Pythagoras' Theorem: d = √(l² + w² + h²). This is an extension of the 2D Pythagoras' Theorem. Understanding this concept is crucial for solving three-dimensional problems, calculating distances across boxes, rooms, or cuboids, and visualising geometric relationships. Practising space diagonal problems builds spatial reasoning, essential for GCSE questions and real-world applications like construction, design, and navigation.