12 multiple-choice questions, progressively harder.
The construction sketch shows the solid circle centered at OOO and a dashed circle. Which segment is a diameter of the dashed circle?
Solution
Correct answer: B
The dashed circle is centered at M, and O and P are on its boundary. The diameter through M has length
The center and external point are 464646 mm apart. Which compass opening can draw midpoint arcs that cross in two places?
Correct answer: D
The compass opening must exceed half the length of OP.
An opening of 252525 mm is large enough. Exactly 232323 mm makes one meeting point. A smaller opening makes none.
In the diagram, the compass opening stayed fixed while drawing arcs from OOO and PPP. Why does line UVUVUV bisect OPOPOP?
Correct answer: A
A crossing is one compass opening from O and that same opening from P. Both crossings therefore lie on the perpendicular bisector.
The auxiliary circle already crosses the given circle at T1T_1T1 and T2T_2T2. What is the last straightedge action?
Correct answer: C
Each crossing gives its own point of contact. Join each to P to determine the two lines.
The midpoint MMM of OPOPOP is 999 units from PPP. What is the diameter of the auxiliary circle used to construct the tangents?
The compass opening from M to P is a radius. The diameter has twice that length.
The circles in the diagram cross at T1T_1T1 and T2T_2T2. How would the line through those two points meet the given solid circle?
Both crossings belong to the solid circle. The line through them crosses the circle at each, so it is a secant.
Point TTT is an intersection of the given circle and the circle with diameter OPOPOP. Which angle does that diameter make right at TTT?
The semicircle theorem puts the vertex at T and the endpoints of the diameter on the two rays.
Point PPP coincides with the center OOO of a positive-radius circle. How many tangent lines pass through PPP?
The center-to-point distance is smaller than the positive radius rrr.
Every line through the center cuts a diameter, so each line crosses the circle twice.
Point PPP lies on a ray starting at OOO, beyond that ray's crossing with the given circle. How many tangent lines through PPP can the diameter construction produce?
Call the ray's crossing with the circle A. P is beyond A, so its center distance exceeds the radius.
The auxiliary circle gives two distinct contact points.
At the crossing T2T_2T2, which segment is a radius of the given circle centered at OOO?
A radius of the given circle joins O to a point on that circle. For its radius length rrr,
Point PPP lies on the given circle. Four proposed lines through PPP make angles of 30∘30^\circ30∘, 45∘45^\circ45∘, 60∘60^\circ60∘, and 90∘90^\circ90∘ with ray POPOPO on one side of that ray. Which angle belongs to the tangent?
P is already the contact point, so the tangent line ℓ\ellℓ must be perpendicular to its radius.
After both contact points are located, which tool use extends a tangent segment to a tangent line?
Call the contact point T. The straightedge extends the segment through the two distinct points P and T to the line
Reset this practice set?
This clears every answer you have given and starts the set again from question 1.