Теория:

An altitude of a triangle is the perpendicular line drawn from the vertex of the triangle to the opposite side.  The altitude of a triangle is also known as the height of the triangle.
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In triangle \(ABC\), \(AD\) is the altitude which is a perpendicular line drawn from the vertex \(A\) to the point \(D\) in the opposite side \(BC\).
 
Important!
  • The altitude makes a right angle with the base of a triangle. Here in Δ \(ABC\), \(AD\) is perpendicular to \(BC\).
  • As there are three possible vertices for any triangles, there will be three possible altitudes.