Question

va rog ajutatima !!!!!
dau coroana

Answer 1

8. ΔABC, AM inaltime, M∈[BC]
M mijloc [BC]
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ΔABC isoscel

M mijloc [BC]⇒[BM]≡[MC]
AM inaltime⇒AM⊥BC
ΔAMB≡ΔAMC deoarece au(CC) [BM]≡[MC]      ⇒[AB]≡[AC]⇒ΔABC isoscel
(dreptunghice)                             AM comuna

9. fie ΔABC dreptunghic in A
ΔABC isoscel⇒[AB]≡[AC]
AD inaltime⇒AD⊥BC, D∈BC
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AD=BC/2

ΔABC dreptunghic isoscel⇒m(∡B)=m(∡C)=45°
AD⊥BC⇒m(∡ADB)=m(∡ADC)=90°⇒ΔADB si ΔADC dreptunghice in D
ΔADB dreptunghic in D si m(∡B)=45°⇒ΔADB dreptunghic isoscel⇒[AD]≡[BD]
ΔADC dreptunghic in D si m(∡C)=45°⇒ΔADC dreptunghic isoscel⇒[AD]≡[CD]
BC=BD+CD=AD+AD=2AD
AD=BC/2

10. ΔABC isoscel, BC baza⇒[AB]≡[AC]
  BD inaltime⇒BD⊥AC
  CE inaltime⇒CE⊥AB
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[BD]≡[CE]

ΔABC isoscel⇒∡B≡∡C
ΔBDC≡ΔCEB deoarece au (CU) BC comuna⇒[BD]≡[CE]
dreptunghice                                ∡C≡∡B