You can solve this using the Pythagorean theorem. The Pythagorean therorem states the a^2+b^2(the sides of the triangle adjacent to the right angle) = c^2(the hypotenuse/diagonal) Now lets plot the information into the Theorem. 7^2+b^2=8.6^2 Solve for b 49+b^2=73.96 b^2=73.96-49 b^2=24.96 b=√(24.96) b=4.99599839872
