how do i calcualte the length of an unknown side of a right angled triangle

To calculate the length of the unknown side you must know the lenght of two of the other sides of the right angled triangle. if we know this we can use pythagoros thereom. The equation for this is a^2+b^2=c^2. where a and b are the lenghts of the two shorter sides and c is the lenght of the longest side which is always oppisite the largest angle in a triangle which in this case is opposite the right angle because the triangle is a right angled triangle. So if we wanted to calculate the length of the hypotenuse which is the largest side, we would substitute the values of the lengths of the two other sides to where a and b are in the equation. This will give us the value of c^2 so then we will square root this value to find the value of the length of the longest side.