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In a circle, let AB = CD = 12 be two chords that intersect at point P. Given that ∠APC = 60° and AC = 2BD, find the values of AC, CP, and PA.

User SvenFinke
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Final answer:

In this problem, we are given two intersecting chords in a circle and some information about the angles and lengths of the chords. By using properties of intersecting chords and similar triangles, we can solve for the values of AC, CP, and PA.

Step-by-step explanation:

Let's use some properties of intersecting chords in a circle to solve this problem.

First, we know that the angle between two intersecting chords is half the sum of the arcs they cut off.

In this case, ∠APC is 60°, so arc ACB measures 120°.

Also, we are given that AC = 2BD. Since AB = CD = 12, we can calculate AC = 24 and BD = 6.

Now, since arc ACB measures 120°, it means that arc AB measures 240°. Therefore, arc AD measures 360° (full circle) minus 240° which is 120°.

Since AD is an arc of length 12, we can calculate the circumference of the circle by setting up a proportion:

(circumference of the circle) / 360 = 12 / 120

Solving this proportion, we find the circumference to be 120π, which means the radius of the circle is 20π.

Finally, using the radius, we can find the length of AC by multiplying the radius by the central angle it subtends:

length of AC = (radius of the circle) * (∠ACB / 360) = 20π * (120° / 360) = 20 * (120° / 180) = 40.

So, AC = 40.

Similarly, we can find the lengths of CP and PA by using similar triangles.

Let's denote the intersection point of AC and BD as E. Triangle ACD and triangle BDC are similar since angle ACD is equal to angle BDC (both are vertical angles) and angle CAD is equal to angle CBD (both are inscribed angles that intersect the same arc AD).

Therefore, we can set up a proportion:

CP / BD = AC / CD

Substituting the given values, we get CP / 6 = 40 / 12

Simplifying this proportion, we find CP = 20.

Similarly, we can set up another proportion:

PA / CD = AC / BD

Substituting the given values, we get PA / 12 = 40 / 6

Simplifying this proportion, we find PA = 80.

So, the values of AC, CP, and PA are 40, 20, and 80, respectively.

User Nubela
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