Prove Parallelogram Point P's Angles are Equal

In summary, a parallelogram is a quadrilateral with two pairs of parallel sides and has properties such as equal and parallel opposite sides, equal opposite angles, and supplementary consecutive angles. To prove that Point P's angles in a parallelogram are equal, you can use the theorem that states "If a quadrilateral is a parallelogram, then its opposite angles are equal." Other methods to prove a quadrilateral is a parallelogram include showing parallel and equal opposite sides, equal opposite angles, supplementary consecutive angles, and bisected diagonals. Proving Point P's angles in a parallelogram are equal is important for understanding geometry and making accurate calculations and predictions in real-world situations.
  • #1
Albert1
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View attachment 972
Point P is an iner point of a parallelogram ABCD
given $\angle PAB=\angle PCB$
please prove :$\angle PBA=\angle PDA$
 

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  • #2
View attachment 986
Construct P'C//PB , and P'P//BC ,connecting P'D
now
BCP'P and APP'D are two parallelograms
it is easy to see
$\angle P'DC=\angle PAB=\angle PCB=\angle P'PC$
four points C,P'D,P are cyclic
$\therefore \angle DPP'=\angle DCP'$
but $\angle PDA=\angle DPP' , and\,\, \angle DCP'=\angle PBA \therefore \angle PBA=\angle PDA$
 

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Last edited:

1. What is a parallelogram?

A parallelogram is a quadrilateral with two pairs of parallel sides. This means that opposite sides of a parallelogram are always equal in length and parallel to each other.

2. What are the properties of a parallelogram?

The properties of a parallelogram include: opposite sides are parallel and equal in length, opposite angles are equal, consecutive angles are supplementary (add up to 180 degrees), and the diagonals bisect each other.

3. How do you prove that Point P's angles in a parallelogram are equal?

To prove that Point P's angles in a parallelogram are equal, you can use the theorem that states: "If a quadrilateral is a parallelogram, then its opposite angles are equal." This means that if you can show that the quadrilateral is a parallelogram, then you can automatically prove that Point P's angles are equal.

4. What are some methods to prove that a quadrilateral is a parallelogram?

There are a few methods to prove that a quadrilateral is a parallelogram, including: showing that opposite sides are parallel and equal in length, showing that opposite angles are equal, showing that consecutive angles are supplementary, and showing that the diagonals bisect each other. You can also use the properties of a parallelogram to prove that it is a parallelogram.

5. Why is it important to prove that Point P's angles in a parallelogram are equal?

Proving that Point P's angles in a parallelogram are equal is important because it helps us understand the properties of parallelograms and build upon our knowledge of geometry. It also allows us to make accurate calculations and predictions in real-world situations that involve parallelograms, such as building structures and designing objects.

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