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Fie dreptunghiul ABCD cu AB=6 cm si BC=4cm.Perpendiculara in C pe AC intersecteaza dreapta AD in M.Aflati lungimea segmentului AM.

Răspuns :

Aplic teorema lui Pitagora in triunghiul ABC-dreptunghic in B:
[tex] AB^{2}+ BC^{2}= AC^{2}=>AC= \sqrt{AB^{2}+BC^{2}}= \sqrt{36+16}= \sqrt{52}= \\ = 2\sqrt{13} (cm). [/tex]

Fie {E}=MC ∩ AB.

Aplic teorema inaltimii in ΔACE-dreptunghic in C:
[tex] BC^{2}=AB*BE=>BE= \frac{BC^{2}}{AB}= \frac{16}{6}= \frac{8}{3}(cm). [/tex]

Aplic teorema lui Pitagora in ΔBEC-dreptunghic in B:
[tex] BC^{2}+ BE^{2}= CE^{2} =>CE= \sqrt{ BC^{2}+BE^{2} } = \sqrt{16+ \frac{64}{9} }= \sqrt{ \frac{208}{9} } = \\ = \frac{4 \sqrt{3} }{3} (cm).[/tex]

Aplic teorema inaltimii in ΔMAE-dreptunghic in A:
[tex] AC^{2}=MC*CE=>MC= \frac{AC^{2}}{CE}= \frac{52}{ \frac{4 \sqrt{3} }{3} }= \frac{52*3}{ 4\sqrt{3} }= \frac{39}{ \sqrt{3} }= \frac{39 \sqrt{3} }{3}= \\ 13 \sqrt{3}(cm). [/tex]

ME=MC+CE=[tex] 13\sqrt{3}+ \frac{4 \sqrt{3} }{3}= \frac{43 \sqrt{3} }{3} (cm).[/tex]

Aplic teorema lui Pitagora in ΔMAE-dreptunghic in A:
[tex] AM^{2}+ AE^{2}= ME^{2}=>AM= \sqrt{ME^{2}-AE^{2}}= \sqrt{ \frac{1849}{3}- \frac{676}{9} }= \\ = \sqrt{ \frac{4871}{9} }= \frac{ \sqrt{4871} }{3}(cm). [/tex]