Show the techniques necessary to prove that a line is perpendicular to a plane .

There are several methods in order to prove that a line is perpendicular to a plane (P):

-there is a line d1 perpendicular to a line d, where d belongs to (P) => d1 is perpendicular to (P), too.

- d parallel to another line d1, where d1 is perpendicular to (P), so d is perpendicular to (P), too.

- d is perpendicular to a plane (Q), where (Q) is also parallel to (P), so d is perpendicular to (P), too.

- there are 2 concurrent lines, a and b, which belong to (P), d is perpendicular to a and d is perpendicular to b,  so d is perpendicular to (P), too.