In Euclidean plane geometry every triangle MUST BE coplanar.
It means 3 angles that can be found in a triangle.
yes
In normal geometry, it's not possible to make a triangle with two obtuse angles. It is possible to make a triangle with two obtuse angles in spherical geometry -- it's a kind of "spherical triangle". It is possible to make a triangle with two obtuse angles in some kinds of non-Euclidean geometry -- it's a kind of "non-Euclidean triangle".
One example of analogy reasoning in geometry is when you have to figure out what type of triangle a triangle is. For example, if you have a triangle with three sides and you can tell the sides are the same size, you can deduce you have an equilateral triangle, even without measuring it.
A right triangle in geometry is a triangle that has 90 degrees as one of its angles.
The answer will depend on what PARTS! Also, you will not be able to go very far without a good understanding of spherical geometry.
The altitude of a triangle IS a geometric concept so it intersects geometry in its very existence.
Corresponding parts of congruent triangles are congruent, perhaps some people use equal instead of congruent?
No, never in plane geometry.
In geometry, magnitude is the length of the hypotenuse of a right triangle.
He drew a triangle on his geometry test.
In Euclidean plane geometry every triangle MUST BE coplanar.
It means 3 angles that can be found in a triangle.
The longer sides of a triangle
yes
In normal geometry, it's not possible to make a triangle with two obtuse angles. It is possible to make a triangle with two obtuse angles in spherical geometry -- it's a kind of "spherical triangle". It is possible to make a triangle with two obtuse angles in some kinds of non-Euclidean geometry -- it's a kind of "non-Euclidean triangle".