SOLUTION: Thank you for your help in advance. Choose a proof to complete from the options below. Use either a Two-column Proof, Paragraph Proof, or Flow Chart Proof to complete your work

Algebra ->  Geometry-proofs -> SOLUTION: Thank you for your help in advance. Choose a proof to complete from the options below. Use either a Two-column Proof, Paragraph Proof, or Flow Chart Proof to complete your work      Log On


   



Question 1081439: Thank you for your help in advance.
Choose a proof to complete from the options below.
Use either a Two-column Proof, Paragraph Proof, or Flow Chart Proof to complete your work. Be sure to include all logical steps if you include a picture or drawing.
Prove the opposite angles of a parallelogram are congruent.
Prove the base angles of an isosceles triangle are congruent.

Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

Start with the following isosceles triangle. The two equal sides are shown with one red mark and the angles opposites to these sides are also shown in red.

Image and video hosting by TinyPic


The strategy is to draw the perpendicular bisector from vertex C to segment AB.
Then use SAS postulate to show that the two triangles formed are congruent.
If the two triangles are congruent, then corresponding angles to will be congruent.
Draw the perpendicular bisector from C.

Image and video hosting by TinyPic

Since angle C is bisected,we got
angle x and angle y which are same measure; so, angle +x=+y
Segment AC+=++BC... ( This one was given)
Segment CF+=+CF+(Common side is the same for both triangle ACF and triangle BCF)
Triangles ACF and triangle BCF are then congruent by SAS or side-angle-side.
In other words, by
AC-angle(x)-CF
and
BC-angle(y)-CF
Since triangle ACF and triangle BCF are congruent, angle A = angle+B