An indirect proof is a proof by contradiction.
The proof is pretty simple, but hard to see without the pictures. SO here is a link to the proof with some pics. http://www.apronus.com/geometry/triangle.htm The answer depends on your geometry: In Euclidean geometry, the angle sum is 180 degrees, in Hyperbolic geometry it is less than 180 degrees, and in Elliptical geometry it is greater than 180 degrees.
Theorems is what is proven with the geometric proof.
One of the fundamental assumptions made in Euclidean Geometry is that space is flat. This is not true. Albert Einstein was able to show, both in mathematical proof and in actual demonstration, that space was curved.Euclidean geometry, as Euclid intended it, also assumes 2 or 3 dimensions of space. Euclidean geometry has been extended since then to arbitrary dimensions, though many physicists now believe that space has a full 11 dimensions.
Euclidean geometry, non euclidean geometry. Plane geometry. Three dimensional geometry to name but a few
True (apex)
A direct proof in geometry is a proof where you begin with a true hypothesis and prove that a conclusion is true.
Theorems are statements in geometry that require proof.
I am not really sure what you are asking but there are 3 types of proofs in geometry a flow proof, a 2-collumn proof, and a paragraph proof.
contradiction
contradiction
A proof that uses techniques from geometry.
An indirect proof is a proof by contradiction.
Mathematicians do proof in order to solve Geometry theorems.
An axiom.
There is a beautiful proof of Euler's Therom, using the area of the sphere and spherical geometry.
Once you familiarize yourself with the basic axioms and theorems of geometry, you will be able to see how they apply to the proof of any particular problem that you may be working on.