We can use the same formula to find the length of a short side, knowing the length of the hypotenuse and the length of the other short side. The only difference when finding a short side is that we can put the numbers in the wrong way around if we aren't careful.
The most important thing to remember when finding a short side is that the two lengths need to go into different parts of the formula.
If you get the lengths around the wrong way, you will probably end up with the square root of a negative number (and a calculator error).
We can also rearrange the equation before we perform the substitution, to find formulas for each side length.
To find a shorter side: a^{2}=c^{2}-b^{2} or b^{2}=c^{2}-a^{2}. We can take the square root of both sides to give us the following formulas: a=\sqrt{c^{2}-b^{2}} or b=\sqrt{c^{2}-a^{2}}.
Find the length of the unknown side s in the triangle below. Give the answer as a surd.
Rearranging the Pythagoras' theorem to find a shorter side: a^{2}=c^{2}-b^{2} \,\,\text{ or }\,\, b^{2}=c^{2}-a^{2}We can take the square root of both sides to give us the following formulas: a=\sqrt{c^{2}-b^{2}} \,\,\text{ or }\,\, b=\sqrt{c^{2}-a^{2}}