How to find unknown sides of a triangle using the Rule of Pythagoras.
This topic shows you the
steps for finding unknown sides of right angled triangles using the rule of
The rule of Pythagoras states that in any right angled triangle with legs
‘a’ and ‘b’ and hypotenuse ‘c’,
This rule can be used (a)
to find the hypotenuse, given the two leg lengths, or (b) to find an
unknown leg length, given one of the legs and the hypotenuse.
This is how these problems can be solved...
(a) find the hypotenuse, ‘c’, given legs ‘a’ and ‘b’ of a right triangle:
(b) find leg, ‘b’, given leg ‘a’ and hypotenuse ‘c’ of a right triangle.
Maths Helper Plus shows you to how to solve your own right triangles for unknown sides by using the rule of Pythagoras. The steps below will show you how.
Step 2 Display the parameters box
Press the F5 key to display the parameters box:
You enter the given information into these edit boxes as follows:
edit box 'A' = horizontal leg of the right triangle
edit box 'B' = vertical leg of the right triangle
edit box 'C' = hypotenuse of the right triangle
Set any two of A, B and C to the values you are given.
Set the unknown value to zero.
Out of the three edit boxes A, B and C, two will not be zero, and one will be zero.
NOTE: In the diagram of the parameters box above, A=3, B=4, and C=0. This means we are solving the problem type where the two legs of the right triangle are given, and we are calculating the length of the hypotenuse.
Click the 'Update' button to refresh the diagram and calculations.
Step 3 Adjust the size of the diagram
If the triangle diagram is too big to display properly on your computer screen, briefly press the F10 key to reduce its size. To make the diagram bigger, hold down a Ctrl key while you press F10.