Given a triangle ABC having BAC = 1200, and AC= 2AB. The line passing through A perpendicular to AC intersects the perpendicular bisector of BC at O. Prove that the triangle OBC is an equilateral triangle
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1. Two bisector BD and CE of the triangle ABC intersect at O. Suppose that BD.CE 2BO.OC . Denote by H the point in BC such that .OH⊥BC . Prove that AB.AC 2HB.HC 2. Given a trapezoid ABCD with the based edges BC3cm , DA6cm ( AD//BC ). Then the length of the line EF ( Ein AB,Fin CD and EF // AD ) through the intersection point M of AC and BD is ............... ? 3. Let ABC be an equilateral triangle and a point M inside the triangle such that MA^2MB^2+MC^2 . Draw an equilateral triangle ACD whe...
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1. Two bisector BD and CE of the triangle ABC intersect at O. Suppose that BD.CE = 2BO.OC . Denote by H the point in BC such that .\(OH⊥BC\) . Prove that AB.AC = 2HB.HC
2. Given a trapezoid ABCD with the based edges BC=3cm , DA=6cm ( AD//BC ). Then the length of the line EF ( \(E\in AB,F\in CD\) and EF // AD ) through the intersection point M of AC and BD is ............... ?
3. Let ABC be an equilateral triangle and a point M inside the triangle such that \(MA^2=MB^2+MC^2\) . Draw an equilateral triangle ACD where \(D\ne B\) . Let the point N inside \(\Delta ACD\) such that AMN is an equilateral triangle. Determine \(\widehat{BMC}\) ?
4. Given an isosceles triangle ABC at A. Draw ray Cx being perpendicular to CA, BE perpendicular to Cx \(\left(E\in Cx\right)\) . Let M be the midpoint of BE, and D be the intersection point of AM and Cx. Prove that \(BD⊥BC\)
Let P be the intersection point of 3 internal bisectrices of a given triangle ABC. The line passing through P and perpendicular to CP intersects AC and BC at M and N. If AP=3cm, BP=4cm, compute AM/BN?
Ta có
\(\widehat{ABM}=\widehat{APC}-\widehat{MPC}=\left(90+\frac{\widehat{ABC}}{2}\right)-90=\widehat{PBC}\)
Tương tự tra có: \(\widehat{NPB}=\widehat{PAM}\)
\(\Rightarrow\Delta MAP\approx\Delta NPB\)
\(\Rightarrow\frac{AP}{PB}=\frac{MA}{NP}=\frac{MP}{NB}\)
\(\Rightarrow MA.NB=NP.MP=NP^2=MP^2\)(Dễ thấy tam giác MNC cân có CP là đường cao và đường phân giác)
Ta lại có: \(\frac{MA}{NB}=\frac{MA^2}{MA.NB}=\frac{MA^2}{NP^2}=\frac{AP^2}{PB^2}=\frac{3^2}{4^2}=\frac{9}{16}\)
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Let ABC be a triangle with AB = 3cm, AC = 7cm. The internal bisector of the angle BAC intersects BC at D. The line passing through D and parallel to AC cuts AB at E. Find the measure of DE. Answer: DE = ..........cm.
Let ABC be a triangle with AB = 3cm, AC = 7cm. The internal bisector of the angle BAC intersects BC at D. The line passing through D and parallel to AC cuts AB at E. Find the measure of DE.
Answer: DE = ..........cm.
Write your answer by fraction in simplest form
ta có:
\(\frac{BD}{DC}=\frac{AB}{AC}=\frac{3}{7}\)( do AD là tia phân giác của \(\widehat{BAC}\))
\(\Rightarrow\frac{BD}{BC}=\frac{3}{11}\)
Ta có:
\(\frac{ED}{AC}=\frac{BD}{BC}=\frac{3}{11}\Rightarrow ED=\frac{3AC}{11}=\frac{3.7}{11}=\frac{21}{11}\)
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Given a right triangle ABC (AB is perpendicular to AC) and tthe bisector BD (D \(\in\) AC). Find the area of ABC if AD = 6cm and CD = 10cm
ta có \(\frac{AB}{AD}=\frac{BC}{DC}\)
mà AB2+AC2=BC2
nên AB =12 ;BC=20
vậy diện h là:96
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8 tháng 1 2022 lúc 21:07
Let I be the incentre of acute triangle ABC with ABne AC. The incircle omegaof ABC is tangent to sides BC, CA and AB at D, E, F respectively. The line through D pependicular to EF meets omegaagain at R. Line AR meets omegaagain at P. The circumcircles of triangles PCE and PBF meet again at Q. Prove that lines DI and PQ meet on the line through A perpendicular to AI.
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Let I be the incentre of acute triangle ABC with \(AB\ne AC\). The incircle \(\omega\)of ABC is tangent to sides BC, CA and AB at D, E, F respectively. The line through D pependicular to EF meets \(\omega\)again at R. Line AR meets \(\omega\)again at P. The circumcircles of triangles PCE and PBF meet again at Q. Prove that lines DI and PQ meet on the line through A perpendicular to AI.
8 tháng 1 2022 lúc 21:07
Let I be the incentre of acute triangle ABC with ABne AC. The incircle omegaof ABC is tangent to sides BC, CA and AB at D, E, F respectively. The line through D pependicular to EF meets omegaagain at R. Line AR meets omegaagain at P. The circumcircles of triangles PCE and PBF meet again at Q. Prove that lines DI and PQ meet on the line through A perpendicular to AI.
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Let I be the incentre of acute triangle ABC with \(AB\ne AC\). The incircle \(\omega\)of ABC is tangent to sides BC, CA and AB at D, E, F respectively. The line through D pependicular to EF meets \(\omega\)again at R. Line AR meets \(\omega\)again at P. The circumcircles of triangles PCE and PBF meet again at Q. Prove that lines DI and PQ meet on the line through A perpendicular to AI.
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23 tháng 3 2022 lúc 22:00
Circle O has diameters AB and CD perpendicular to each other. AM is any chord intersecting CB at N.I is the center of the circle inscribed in triangle AMB. Prove that M, I, D are collinear points
Given acute triangle ABC(AB<AC). O is the midpoint of BC, BM and CN are the altitudes of triangle ABC. The bisectors of angle \(\widehat{BAC}\)and \(\widehat{MON}\)meet each other at D. AD intesects BC at E. Prove that quadrilateral BNDE is inscribed in a circle.s
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