The exterior angle inequality theorem is a triangle theorem.

Since

we know that the exterior angle = the sum of the 2 remote interior

angles by a previous theorem (the exterior angle theorem)... We know

then that the exterior angle must be larger than either of the angles

that need to be added.

It's like saying that since 60 + 40 = 100, then 100 must be larger than either 60 or 40 -or-

100 > 60

100 > 40

Since

we know that the exterior angle = the sum of the 2 remote interior

angles by a previous theorem (the exterior angle theorem)... We know

then that the exterior angle must be larger than either of the angles

that need to be added.

It's like saying that since 60 + 40 = 100, then 100 must be larger than either 60 or 40 -or-

100 > 60

100 > 40