The Pythagoras Theorem states that in a right angled triangle, ‘a’ being the base, ‘b’ being the height and ‘c’ being the hypotenuse of that triangle, then a2+b2=c2
Below is an illustration of this –
Example –
1. if the base of a right angled triangle is 3, the height is 4,then what is the length of its hypotenuse?
Solution – given, a=3, b=4 ,c=?
Using Pythagoras theorem,
a2+b2=c2
32+42=c2
√(9+16) =c
c=5
2. if the hypotenuse of a right angled triangle is 13, the height is 5,then what is the length of its base?
Solution –
given, a=?, b=5 ,c=13
Using Pythagoras theorem,
a2+b2=c2
a2+52=132
a=√(169-25)
a=12
Intuition behind Pythagoras Theorem :
Let’s prove this theorem using the figures.
Draw squares corresponding to each side of the triangle as follows –
If we look at the figure closely, we could reframe the Pythagoras theorem as follows-
The area of 2 squares is equal to the third square.
ie- a2 is the area of the 1st square
b2 is the area of the 2nd square
c2 is the area of the 3rd square
thus, a2+b2=c2
Another proof of Pythagoras theorem can be shown by rearranging the triangles to form 2 squares as follows
If we compare the two squares, we can find that both the squares have a+b side length, thus having the same area.
In each square, four right-angled triangles are used (realigned in a different way though)
So, we can conclude that
area(1st square) =a rea(2nd square)
c2 + 4* (area of a right angled triangle)= a2+b2+4* (area of a right angled triangle)
c2=a2+b2 [cancelling the common terms from both sides]
Thus, pythagoras theorem is proved.