Answer:
Step-by-step explanation:
Given that,
Radius of a cone, r = 13 cm
Slant height of the cone, l = 20 cm
We need to find the surface area of the cone. The formula for the surface area of the cone is given by :
Put all the values,
So, the surface area of the cone is .
so it's obvious, I guess :)
Now, let's prove is not rational number.
Proof by contradiction.
Let assume is a rational number. Therefore it can be expressed as a fraction where and .
is an even number, so must also be an even number, and therefore also must be an even number. So, we can say that , where .
Since is an even number, then also must be an even number. 3 is odd, so for to be an even number, must be an even number, and therefore is an even number.
But if both a and b are even numbers, then it contradicts our earlier assumption that . Therefore is not a rational number.
N is a factor of a number” means n divides exactly into the number.