Just use the definition of geometric mean. Multiply all the numbers together, then take the square root. (In this case, it is the square, or second, root, because there are two numbers; for the geometric mean of three numbers, you take the cubic root, etc.)
12.0
A sphere.
Just use the definition of geometric mean. Multiply the two numbers, then take the square root of the result. (To take the geometric mean of three numbers, multiply all of them, then take the cubic root, etc.)
By definition, yes. Any shape is a geometric shape.
Geometric means (1) "relating to geometry" or (2) "having simple geometric forms such as circles and squares in design or decoration."
A geometric term is a term of geometry.
Yes.
Acute < 90°
3 sided geometric figures
A plane is a flat surface
Since probability is not a geometric concept, there is no definition for it in geometry.