write the following reversible statement as a biconditional:

If two perpendicular lines intersect, they form four 90 degree angles.

-Two intersecting lines are perpendicular if and only if they form four angles.
-Two intersecting, perpendicular lines do not form four angles.
-Four 90 degree angles are formed by intersecting lines.
-Perpendicular lines do not intersect.

I think it's the 3rd choice, but please correct me if I'm wrong.

Four 90 degree angles are formed by intersecting perpendicular lines.

Actually, the correct choice is the first option:

Two intersecting lines are perpendicular if and only if they form four angles.

You are correct! The given statement "If two perpendicular lines intersect, they form four 90-degree angles" can be written as a biconditional statement as "Two intersecting lines are perpendicular if and only if they form four 90-degree angles."

A biconditional statement is formed when you combine a conditional statement ("If two intersecting lines are perpendicular, then they form four 90-degree angles") with its converse ("If two intersecting lines form four 90-degree angles, then they are perpendicular") using the phrase "if and only if." In this case, the biconditional statement states that the perpendicularity of two lines is true if and only if they form four 90-degree angles.

So, the third choice "Two intersecting lines are perpendicular if and only if they form four 90-degree angles" is the accurate biconditional statement for the given reversible statement. Great job!