00:01
So here we have to prove pythagoras theorem.
00:05
So i already made the figure that this is our figure.
00:12
Okay? so this is our figure.
00:16
Now what we see here that this is a triangle a b c, a b c with angle a is goes to 90 degree and there are a perpendicular from a on d, a d, okay? so the triangle a b c, this bigger triangle.
00:34
A b c here it is similar with the triangle a d c y because you can see that this is 90 degree and this angle is also 90 degree okay first thing then the second thing is this angle is x then this angle also must be x y because this is 90 minus y this angle x is nothing but this angle x is nothing but 90 minus y okay this is nothing but 90 minus y okay this is nothing but 90 minus y and this angle also here is nothing but 90 minus y so these two angles both are equal and these two angles must be equal okay so we have these two similar triangles so by the property that the ratio of similar triangles the ratio sides of our similar triangles are same so bc upon ac is equals to ac upon dc okay bc upon ac is equal to ac is equal to ac upon dc okay you can also see that bc here it is bc full length the length opposed to the right angle and in this triangle the length opposed to the right angle is ac okay so this is like this now we have another triangle okay we have another triangle abd is similar to cba okay so abd is similar to cba and we got this also so from first what we get we get we get ac square what we get ac square is nothing but b c into dc okay and a b square okay a b square is nothing but b c into bd okay now what we have to do here we have to add these two equations okay we have to add these two equations so when we add we got on the lhs that ab square plus a c square this is equal to take bc common what we get bd plus dc okay so we get ab square plus ac square is equal to bc and this is also okay you can see this is bd bd bd plus dc this is nothing but bc so this is bc okay so, what we get here, ab square plus ac square is equal to b c square.
03:24
So this is the pythagoras theorem, we have proved it.
03:31
Now example, use of this pythagoras theorem.
03:34
So the example here.
03:38
So this is the example.
03:40
Now let us consider that you have a tower, okay, this is a tower.
03:46
And this is perpendicular to the ground okay so this tower is a perpendicular to the ground okay now this tower is perpendicular to ground now you have to made a wire okay so you have to made a wire show that you know you are standing here okay and you know that the length from foot of the tower to yourself is let us suppose 8 meters...