If by sperical triangle you mean a triangle on the surface of a sphere, you will need 3 dimensional coordinate geometry. Whether you use polar coordinates or linear coordinates will depend on what you want to "solve".
Pythagorean theorum.
It depends on the infoamtion that you have.
You cannot solve for a leg in any triangle without at least one other side.
You will also need the angles so that you can use the Isosceles Triangle Theorems to solve for the base of isosceles triangle when only two sides are given.
If by sperical triangle you mean a triangle on the surface of a sphere, you will need 3 dimensional coordinate geometry. Whether you use polar coordinates or linear coordinates will depend on what you want to "solve".
Area of a triangle = (1/2)(base)(height)
I'm assuming that you mean the area of the triangle. You do not need the entire perimeter. The formula is 1/2 bh. b=base, h=hight
Pythagorean theorum.
It depends on the infoamtion that you have.
You cannot solve for a leg in any triangle without at least one other side.
The disappearances of people that entered the triangle.
You will also need the angles so that you can use the Isosceles Triangle Theorems to solve for the base of isosceles triangle when only two sides are given.
There is not enough information to solve this. You need to know one other length od a side to solve this.
The 3 interior angles of any triangle add up to 180 degrees
The answer depends on what you mean by "mean of triangle". There is no such geometric term.
Base times height divided by 2