Answer:
1533.88261311522
Step-by-step explanation:
<em>Let r be the radius of the (base/circle)</em>
<em>and L be the slant height of the cone</em>
<em>Formula ………………………………………………………………………………………………………</em>
The surface area of a cone = the (curved/lateral) surface area + the base

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L = BC = 36



Question is Incomplete, Complete question is given below.
Prove that a triangle with the sides (a − 1) cm, 2√a cm and (a + 1) cm is a right angled triangle.
Answer:
∆ABC is right angled triangle with right angle at B.
Step-by-step explanation:
Given : Triangle having sides (a - 1) cm, 2√a and (a + 1) cm.
We need to prove that triangle is the right angled triangle.
Let the triangle be denoted by Δ ABC with side as;
AB = (a - 1) cm
BC = (2√ a) cm
CA = (a + 1) cm
Hence,
Now We know that

So;


Now;

Also;

Now We know that




[By Pythagoras theorem]

Hence, 
Now In right angled triangle the sum of square of two sides of triangle is equal to square of the third side.
This proves that ∆ABC is right angled triangle with right angle at B.
Answer:
Step-by-step explanation:
this is a famous triangle :) known as the 3-4-5 triangle...
it has an angle of 53.73... on the side with the 3
and an angle of 36.869... on the side with the 4
hope that helps with what ever the question is :)
D. 48 degrees
on calculator: 2ND SIN (72/97) = about 47.92