Question

B) si C) (sau macar una)
Atentie la indicatie!!!!!

Answer 1

$Inainte~sa~incep~rezolvarea,~voi~enunta~o~proprietate~importanta: \\ \\ "Daca~a~si~b~sunt~doua~drepte~paralele,~atunci~d(A,b)=d(B,a), \\ \\ oricare~ar~fi~A \in a~si~B \in b."$

$b)~Prin~punctul~B~se~traseaza~o~paralela~la~AC,~notata~"d". \\ \\ Fie~S=pr_dC.~Conform~proprietatii~de~mai~sus,~avem: d(B,AC)= \\ \\ =d(S,AC)=BM=3,2~(cm). \\ \\ Fie ~T=pr_dA.~cum~AT \perp d~si~CS \perp d,~rezulta~ca~AT ||CS,~deci \\ \\ ATSC~este~paralelogram~cu~un~unghi~drept \Rightarrow ~ATSC-dreptunghi. \\ \\ d(B,AC)=d(T,AC) \Rightarrow A_{ABC}=A_{TAC}= \frac{A_{ACTS}}{2}= \frac{2,5 \cdot3,2}{2}= 4~(cm^2).$

$c)~Se~foloseste~acelasi~ra.ti.o.na.ment: \\ \\ Se~traseaza~prin~A~o~paralele~la~BC~(sa~o~notam~cu~"d"). \\ \\ Se~considera~pucntele~S=pr_dB~si~T=pr_dC. \\ \\ In~mod~analog~se~demonstreaza~ca~BCTS~este~dreptunghi. \\ \\ Cu~proprietatea~de~mai~sus~se~deduce~faptul~ca~d(A,BC)=d(S,BC) \\ \\ Rezulta~A_{ABC}=A_{SBC}= \frac{A_{BCTS}}{2} = \frac{9,9 \cdot 7,2}{2}= 35,64~(cm^2).$

$Indicatia~mi~se~pare~insa~ciudata~de~vreme~ce~se~cunosc~in~fiecare \\ \\ caz~o~lungime~a~unei~laturi~si~inaltimea~corespunzatoare~ei...$