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Prove: If two circles are tangent internally at point P and the chords

PA
and
PB
of the larger circle intersect the smaller circle at points C and D respectively, then
AB

CD
.

User Xwhyz
by
8.1k points

1 Answer

4 votes

Answer:

Proved

Explanation:

Given:

Two circles are tangent internally at point P and chord PA of the larger circle intersects the smaller circle at B.

Prove: measure of arc PA is equal to measure of arc PB

To better understand this, the diagrams have been attached.

From triangle PQB:

Line PQ and line QB are radius of the smaller circle.

Reason: their line are straight lines drawn from the center of the circle to the circumference of the circle

Line PQ = Line QB

That is, side PQ = side QB

Since side PQ = side QB, it is an isosceles triangle.

Therefore < QPB = <PBQ

From triangle PRA

Line PR = line RA

Side PR = side RA

From triangle PRA:

Line PR and line RA are radius of the bigger circle.

Reason: their line are straight lines drawn from the center of the circle to the circumference of the circle

Line PR = Line RA

Since side PR = side RA, it is an isosceles triangle.

Therefore < RPA = <PAR

Using similar triangles theorem:

Triangle PQB = Triangle PRA

<PBQ = <PAR

Since they are equal, the measure of the arc (angle subtended by the arc) are equal.

Therefore measure of arc PA = measure of arc PB

Hope this helps!

User Aalbahem
by
8.5k points
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