- #1
mathstudent88
- 27
- 0
Here is the problem:
If the diagonals of a quadrilateral intersect each other, then the quadrilateral is convex.
Proof:
Let ABCD be a convex quadrilateral. Since quadrilateral ABCD is convex, A and D are on the same side of line BC, and D and C are on the same side of line AB. Thus D is a member of the int(angle ABC). With the Crossbad theorem, BD intersect AC = {P} where C-P-R. So AC intersect BC = {Q} where D-Q-R. Since A, B, C, D are noncollinear points P=Q. So AC intersect BD = {P} = {Q}. Which proves that AC intersects PR = the empty set. Since a convex quadrilateral has the property that its diagonals intersect then ABCD is conves.
How is this? I really didn't know what to do for it. Can someone please help me with it?
Thank you!
If the diagonals of a quadrilateral intersect each other, then the quadrilateral is convex.
Proof:
Let ABCD be a convex quadrilateral. Since quadrilateral ABCD is convex, A and D are on the same side of line BC, and D and C are on the same side of line AB. Thus D is a member of the int(angle ABC). With the Crossbad theorem, BD intersect AC = {P} where C-P-R. So AC intersect BC = {Q} where D-Q-R. Since A, B, C, D are noncollinear points P=Q. So AC intersect BD = {P} = {Q}. Which proves that AC intersects PR = the empty set. Since a convex quadrilateral has the property that its diagonals intersect then ABCD is conves.
How is this? I really didn't know what to do for it. Can someone please help me with it?
Thank you!