Geometryhard · Past Paper

Two circles touch each other externally at point T. A direct common tangent AB touches the circles at A and B. Find the measure of angle ATB.

A45 degrees
B60 degrees
C90 degrees
D120 degrees

✓ Correct Answer: C90 degrees

A common tangent at T will bisect AB. In the resulting triangles, it can be proven that angle ATB = 90 degrees.

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