The work out the length of the missing side you need to use Pythagoras' theorem which states that the sum of the squares of the two sides, in this case x and 60, is equal to the sum of the square of the hypotenuse. This can be formulated as [tex] a^{2} +b^{2}=c^{2}[/tex]. In this case x can replace a or b (I've replaced a). [tex] x^{2} +b^{2}=c^{2}[/tex] To solve for x rearrange the equation by subtracting [tex] b^{2}[/tex] from both sides: [tex] c^{2} -b^{2}=x^{2}[/tex] Substitute the numbers in: [tex] x^{2} = 61^{2} -60^{2}[/tex] = 3721-3600 = 121 Take the square root of 121 to find x: x =[tex] \sqrt{121} [/tex] = 11cm
