12 multiple-choice questions, progressively harder.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets hypotenuse ABABAB at interior point HHH. The whole hypotenuse is 161616 cm, and AH=7AH=7AH=7 cm. Find CHCHCH exactly.
Solution
Correct answer: C
First recover the other hypotenuse piece.
Thus HB=9HB=9HB=9 cm. Now use both pieces.
The positive root gives CH=37CH=3\sqrt7CH=37 cm. Using the whole 161616 in place of the other piece gives 474\sqrt747, which is the leg CACACA.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets the interior of hypotenuse ABABAB at HHH. Find HBHBHB from the following lengths.
AB=13AB=13AB=13 cm
CA=39CA=\sqrt{39}CA=39 cm
Correct answer: A
The given leg touches AHAHAH.
So AH=3AH=3AH=3 cm. The requested piece is the other one.
Therefore HB=10HB=10HB=10 cm. The altitude would be 30\sqrt{30}30 cm; 39/1039/1039/10 uses a piece where the whole hypotenuse belongs.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets the interior of hypotenuse ABABAB at HHH. Find ABABAB from the following lengths.
CH=12CH=12CH=12 cm
HB=18HB=18HB=18 cm
Correct answer: B
Use the altitude to recover the missing piece.
This gives AH=8AH=8AH=8 cm. Add the two pieces.
Thus the whole hypotenuse is 262626 cm. The 888 is only one piece; adding or multiplying the original givens does not find the whole.
Triangle RSTRSTRST is right at SSS. The perpendicular SDSDSD meets the interior of hypotenuse RTRTRT. Find RSRSRS from the following lengths.
RD=4RD=4RD=4 cm
DT=12DT=12DT=12 cm
Correct answer: D
The hypotenuse is RTRTRT, whose pieces add to 161616 cm. Leg RSRSRS touches RDRDRD, the 444 cm piece.
Taking the positive root gives RS=8RS=8RS=8 cm. The altitude is 434\sqrt343 cm, and the other leg is 838\sqrt383 cm.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets hypotenuse ABABAB at interior point HHH. The pieces satisfy
AH:HB=2:7AH:HB=2:7AH:HB=2:7
AB=27AB=27AB=27 cm. Find CHCHCH exactly.
There are nine equal ratio parts in the whole 272727 cm, so each part is 333 cm.
Use their product.
Thus CH=314CH=3\sqrt{14}CH=314 cm. The sum of the ratio numbers is not a length, and 14\sqrt{14}14 omits the scale of the pieces.
A right triangle and its hypotenuse altitude are enlarged by a dilation with factor 333. How does the altitude length change?
A dilation multiplies every length by its factor. The geometric-mean relation agrees: each hypotenuse piece triples, so their product is multiplied by 999.
Both lengths are positive, giving hnew=3holdh_{\text{new}}=3h_{\text{old}}hnew=3hold. The factor 999 belongs to squared lengths.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets hypotenuse ABABAB at interior point HHH. Use these length names.
a=BCa=BCa=BC
c=ABc=ABc=AB
What is the scale factor from the whole triangle ABCABCABC to triangle CBHCBHCBH, using corresponding hypotenuses?
The ordered similarity is
The original hypotenuse ABABAB matches the image hypotenuse CBCBCB. Image length divided by original length gives
The reciprocal reverses the direction. The other choices use sides that do not correspond in this mapping.
b=CAb=CAb=CA
p=AHp=AHp=AH
q=HBq=HBq=HB
Which statement must hold?
Both squared legs use the same positive whole hypotenuse ccc.
Multiplying by ccc preserves order, and positive lengths have the same order as their squares. Thus the longer leg touches the longer piece: a>ba>ba>b exactly when q>pq>pq>p.
The ratio q/pq/pq/p is the ratio of squared legs. Taking its positive square root gives a/ba/ba/b.
h=CHh=CHh=CH
Which equation expresses the altitude relation using only these three lengths?
The missing piece is the whole minus AHAHAH.
The altitude uses the two pieces.
The products cpcpcp and c(c−p)c(c-p)c(c−p) give the squares of the legs. The sum p+cp+cp+c does not express the altitude relation.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets the interior of hypotenuse ABABAB at HHH. A student uses the following givens.
AB=10AB=10AB=10 cm
AH=4AH=4AH=4 cm
They write BC2=10⋅4BC^2=10\cdot4BC2=10⋅4. What is the correct value of BCBCBC?
The 444 cm piece touches CACACA, not BCBCBC. The piece at BBB is
Thus HB=6HB=6HB=6 cm, giving
The positive root is BC=215BC=2\sqrt{15}BC=215 cm. The wrong product gives CACACA; 24\sqrt{24}24 is the altitude.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets hypotenuse ABABAB at interior point HHH. Suppose AH=HBAH=HBAH=HB. Which expression equals CHCHCH in terms of ABABAB?
The equal pieces each have length AB/2AB/2AB/2. Their geometric mean is the same positive number.
Therefore CH=AB/2CH=AB/2CH=AB/2. No special-triangle ratio is needed; this follows directly from the altitude relation.
Triangle ABCABCABC is right at CCC. The altitude CHCHCH meets the interior of hypotenuse ABABAB at HHH. For a positive number xxx, the lengths are as follows.
AH=4xAH=4xAH=4x cm
HB=9xHB=9xHB=9x cm
CH=18CH=18CH=18 cm
Find ABABAB.
Substitute the two pieces into the altitude relationship.
Since xxx is positive, 6x=186x=186x=18, so x=3x=3x=3. Add the pieces.
Thus AB=39AB=39AB=39 cm. The 131313 omits the common scale, 181818 is the altitude, and 117117117 uses x2x^2x2 in a length.
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