Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 1 - No. 5)
What do you need to know to calculate the third side of a right-angled triangle?
The lengths of the other two sides.
The measure of at least one other angle (other than the right angle).
The area of the triangle.
The formula for the Pythagorean theorem.
Forklaring
The lengths of two sides are needed to find the missing side.