中三数学几何证明题~有图1.ΔABC is a right-angled triangle with∠BAC=90度.AF is perpendicular to BC.D is a point on ACsuch that BD=DC=FC=1.what is the length of AC.2.InΔABC,∠ACB=120度.CH perpendicular AB.GIVEN THAT CA+AH=HB.FIND∠B3.
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中三数学几何证明题~有图1.ΔABC is a right-angled triangle with∠BAC=90度.AF is perpendicular to BC.D is a point on ACsuch that BD=DC=FC=1.what is the length of AC.2.InΔABC,∠ACB=120度.CH perpendicular AB.GIVEN THAT CA+AH=HB.FIND∠B3.
中三数学几何证明题~有图
1.ΔABC is a right-angled triangle with∠BAC=90度.AF is perpendicular to BC.D is a point on AC
such that BD=DC=FC=1.what is the length of AC.
2.InΔABC,∠ACB=120度.CH perpendicular AB.GIVEN THAT CA+AH=HB.FIND∠B
3.AREA OF ΔABK=6,BD:DC=3:5 AND AK;KD=4;5.FIND THE AREA OFΔCDK
4.IN ΔABC,∠C=90度,D AND E ARE POINT ON AB.GIVEN THAT AE=AC,∠DCE=45度.FIND THE SEGMENT HAVING THE SAME LENGTH AS BC
5.the area ofΔABC IS 10.POINT D,E AND F ARE ON AB,BC AND CA RESPECTIVELY SUSH THAT AD=2,DB=3.IF AREA OFΔABE EQUALS AREA OF DBEF WHAT IS THE AREA OFΔABE
6ΔABC IS A RIGHT-ANGLED TRIANGLE WITH∠BCA=90度.THE MEDIAN CM IS PERPENDICULAR TO MEDIAN BN.IF BC =1,WHAT IS THE LENGTH OF BN.
中三数学几何证明题~有图1.ΔABC is a right-angled triangle with∠BAC=90度.AF is perpendicular to BC.D is a point on ACsuch that BD=DC=FC=1.what is the length of AC.2.InΔABC,∠ACB=120度.CH perpendicular AB.GIVEN THAT CA+AH=HB.FIND∠B3.
(1).作DE⊥BC于E.∵BD=DC,∴DE是BC的中垂线.
设AD=x.∵AC^2=FC*BC,∴BC=(1+x)^2.
∵AC/BC=(BC/2)/CD,∴(1+x)/(1+x)^2=(1+x)^2/2,
(1+x)^3=2,AC=1+x=立方根2.
(2).延长BA到D,使AD=AC.HB=CA+AH=DA+AH=DH,
∠B=∠D=∠DCA,∠B+∠D+∠DCA+∠ACB=180,∠B=20度.