Given:
The right angled triangle ABC,
Length of side AB=7
Length of side AC=8
Objective is to find length of side BC.
By using pythagorean thorem,
[tex]\begin{gathered} AC^2=AB^2+BC^2 \\ 8^2=7^2+BC^2 \\ BC^2=8^2-7^2 \\ BC^2=15 \\ \text{taking square root on both side,} \\ BC=\sqrt[]{15} \\ BC=3.9 \end{gathered}[/tex]
Answer: the length of 3rd side BC=3.9
