Question

Point P is outside a circle with center O and is 10 cm from the center. The circle has a radius of 5 cm. Lines PA and PB are two different lines tangent to the circle at points A and B.

Find the measure of angle PAO. Round to the nearest whole degree

Find the measure of angle APO. Round to the nearest whole degree

Find the measure of angle AOB. Round to the nearest whole degree

Find PB rounded to the nearest tenth.

Answer 1

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Answer:

• ∠PAO = 90°
• ∠APO = 30°
• ∠AOB = 120°
• PB ≈ 8.7

Explanation:

A tangent makes a right angle with the radius to the point of tangency. Hence ∠PAO is 90°. The ratio of the short side (OA) of the right triangle OAP to the hypotenuse (OP) is 5 : 10 = 1 : 2. These are the ratios found in a 30°-60°-90° triangle, so we know that ∠APO = 30°.

OP is a bisector of angle APB, so that angle is 60°. Angle AOB is the supplement to angle APB, so ∠AOB = 120°.

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As we said above, triangle OAP is a 30°-60°-90° triangle, so its side lengths have the ratios 1 : √3 : 2. This means PA = PB = 5√3 ≈ 8.7.