Question from the lawyer:  "Dr. Expert, I only see a 70° angle here, Exhibit A.  Kelly said that having this angle means you have a plane.  From what I see, none of the definition of a plane say that an angle defines a plane.  Explain how each definition proves that an angle defines a plane." 14. Definition 1: Three points that are not collinear.      
Proof:

15. Definition 2: A line and a point not lying on the line.
Proof:

16. Definition 3: Two lines which intersect     
Proof:

I need help with the proof :)

14. Three points tat are not collinear

Three points that are not colinear consist of a line and a third point, therefore, joining all three points form a flat figure having a length and a width which is a two-dimensional flat figure or a plane

15. A line and a point not lying on the line

Like the example above, the joining of the points results in a two dimensional figure having a length and a width also known as a planar surface

16. Two lines which intersect at a point

Given two lines that intersect at a point, joining the other end point of the two lines results in the forming of a flat figure, that can be described in two dimensions also known as a planar surface or plane

Step-by-step explanation:

A plane in mathematics is a flat surface that has only two dimensions and extends infinitely in all directions

step-by-step explanation :

we know that

the measurement of the outer angle is the semi-difference of the arcs which comprises

in this problem

m< xzy is the outer angle

substitute the values

the measure of angle xoy is equal to

> by central angle

substitute the value