What is the way to write geometry proofs?
A recommendation is below.
Start with known (given) information.
"Given an isosceles triangle".
Then specify, what is to be proven.
"Prove that the median to its base is also an altitude".
Then it is useful to draw a picture of what's given with labels to each element involved.
Add elements needed for the proof you'd like to offer.
"Draw a median
Then specify logical statements, each having a known fact, derived conclusion and the logical basis this conclusion is founded upon in some (not necessarily this) order.
It is important to preserve the logic of derivation that leads, step by step, from given information to a statement that necessary to prove, so each subsequent step is based only on known and proven statements.
Of course, certain fundamental theorems studied before should be considered as proven and can be a foundation for logical derivation.
(2) Since triangles
(3) Since angles
End of proof