19:25 Câu 1:
A man drove a car from A to B at speed 60km/h. After arriving B, he took a rest for 30 minutes then turned back to A at speed 40km/h. Known that he started from A at 7:00 am and he reached A again at 3:15pm on the same day. The distance between A and B is km. Câu 2:
The minimum of the expression
Given that
The sum of such integers
Given two triangles
If
How many real numbers
Answer: There are numbers
The operation
ABC is a triangle. AM is the bisector of angle CAB. Given that AM = 4cm, AB = 6m and AC = 12cm.Then the measurement of angle BAC is degrees. Câu 8:
The number of pairs
Given that
Calculate:
(Input the answer as a decimal in its simplest form) Nộp bài
câu 7 mk bấm nhầm đáp án là 120
qua B kẻ đường thẳng song song với AM cắt AC ở N.
vì AM là phân giác góc BAC nên có :
\(\dfrac{AC}{AB}=\dfrac{CM}{BM}=\dfrac{12}{6}=2\) suy ra \(\dfrac{CM}{BC}=\dfrac{CM}{CM+BM}=\dfrac{12}{12+6}=\dfrac{2}{3}\)
vì AM song song với BN nên có :
1,\(\dfrac{CA}{AN}=\dfrac{CM}{BM}=\dfrac{12}{AN}=2\) suy ra AN=6
2,\(\dfrac{AM}{BN}=\dfrac{CM}{BC}=\dfrac{2}{3}=\dfrac{4}{BN}\)suy ra BN=6
vì AB=6 nên tam giác ABN đều
suy ra \(\widehat{NAB}\)=\(60^0\)
mà \(\widehat{NAB}+\widehat{BAC}=\)\(180^0\)
nên \(\widehat{BAC}=\)\(120^0\)
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