[tex]\Delta ABC[/tex]
[tex]A(1,2),B(3,-1),C(1,-2)[/tex]
[tex]Fie \: h_{A} \: inaltimea \: din \: A=>h_{A} \perp BC[/tex]
[tex]Fie\:m_{BC} \: panta \: lui \: BC[/tex]
[tex]m_{BC}:\frac{y_{C}-y_{B}}{x_{C}-x_{B}}[/tex]
[tex]m_{BC}: \frac{ - 2 - ( - 1)}{1 - 3} [/tex]
[tex]m_{BC}: \frac{ - 2 + 1}{ - 2} [/tex]
[tex]m_{BC}: \frac{ - 1}{ - 2} [/tex]
[tex]m_{BC}: \frac{1}{2} [/tex]
[tex]h_{A}\perp BC=>m_{h_{A}}\times m_{BC}=-1[/tex]
[tex]m_{h_{A}} \times \frac{1}{2} = - 1[/tex]
[tex]m_{h_{A}} = - \frac{1}{ \frac{1}{2} } [/tex]
[tex]m_{h_{A}} = - 2[/tex]
[tex]h_{A}:y-y_{A}=m_{h_{A}}(x-x_{A})[/tex]
[tex]h_{A}:y - 2 = - 2(x - 1)[/tex]
[tex]h_{A}:y - 2 = - 2x + 2[/tex]
[tex]h_{A}:2x + y - 2 - 2 = 0[/tex]
[tex]h_{A}:2x + y - 4 = 0[/tex]