Answer:
If you don't have a protractor handy, you can determine the size of an angle using the basic geometric principles of triangles. You'll need a scientific calculator to solve the equations. Most smartphones are equipped with them, but you can also download a free app or access a free calculator online.
Let's plug the coordinate point values into the equation:

(1,3) is
x₁ and (3,1) is x₂
Begin to simplify within the parenthesis:

Square the two numbers:
Add the two to get:
Since 8 is not a square number, this is as far as we can simplify this. Hope this helps!
Answer:
1
Step-by-step explanation:
If we have n angle the formula for the sum of internal angles is:
sum = 180*(n-2)
in this case n=10,
so the answer will be 180 * 10 = 1800