12 multiple-choice questions, progressively harder.
A falling straight line gives one slope triangle with signed rise −4-4−4 and run 6. A second slope triangle has run 15. What is its signed rise?
Solution
Correct answer: C
AA similarity fixes the rise-to-run ratio. Let the second signed rise be hhh.
The negative sign agrees with a fall to the right.
Which equation describes the line through (2,−4)(2,-4)(2,−4) perpendicular to 3x+5y=83x+5y=83x+5y=8?
Correct answer: A
The given slope is −3/5-3/5−3/5, so the required slope is 5/35/35/3.
The point satisfies the equation and the slopes multiply to −1-1−1.
What is the perpendicular bisector of the segment from (−6,1)(-6,1)(−6,1) to (2,5)(2,5)(2,5)?
Correct answer: D
Its midpoint is (−2,3)(-2,3)(−2,3) and its segment slope is 1/21/21/2. The perpendicular direction therefore has slope −2-2−2.
A segment has endpoints (4,−7)(4,-7)(4,−7) and (4,1)(4,1)(4,1). What is its perpendicular bisector?
Correct answer: B
The midpoint is (4,−3)(4,-3)(4,−3). A perpendicular to the vertical segment is horizontal, so it fixes the midpoint's second coordinate.
Triangle ABCABCABC has
Which is the median line from CCC?
The midpoint of ABABAB is (2,1)(2,1)(2,1). The median slope is 7/47/47/4, so
Both (2,1)(2,1)(2,1) and C=(6,8)C=(6,8)C=(6,8) satisfy the result.
Find the altitude line from A=(1,7)A=(1,7)A=(1,7) in the triangle with
The opposite side has slope 1/21/21/2. The altitude has slope −2-2−2 and contains AAA.
A triangle's median line and another vertex's altitude line have equations
Where do they meet?
A common point must give the same height in both equations.
Substitution of (3,−3)(3,-3)(3,−3) works in both lines.
For which value of kkk are the lines below distinct and parallel?
The slopes are −k/4-k/4−k/4 and −3/2-3/2−3/2. Equating them gives
Their intercepts are 9/49/49/4 and 1/21/21/2, so they are distinct.
In a triangle, vertex B=(6,−1)B=(6,-1)B=(6,−1) and side ACACAC has slope 3. Which equation is the altitude line from BBB?
The perpendicular direction has slope −1/3-1/3−1/3. Through BBB,
The slope and point conditions both hold.
Segment ABABAB has midpoint M=(1,4)M=(1,4)M=(1,4) and endpoint A=(−3,6)A=(-3,6)A=(−3,6). Its perpendicular bisector is y=2x+2y=2x+2y=2x+2. Which is BBB?
Reflect the endpoint's coordinates across the midpoint coordinatewise.
The resulting segment slope is −1/2-1/2−1/2 and the given bisector slope is 2, checking perpendicularity.
A slope triangle has run 8 and signed rise −6-6−6. Which slope comes from rotating it 90∘90^\circ90∘ counterclockwise?
The rightward run becomes rise 8, and the downward rise becomes run 6 right.
The original slope is −3/4-3/4−3/4, the negative reciprocal of this value.
Which statement about its median and altitude lines from AAA is correct?
The median is
and the altitude is
The midpoint of BCBCBC is (2,1)(2,1)(2,1), so the line joining it to AAA is vertical. The side BCBCBC is horizontal, so the altitude from AAA is the same vertical line.
The two definitions can select one line in this configuration.
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