Editing Altitude (triangle) (section)

===Circumradius theorem===

Denoting the altitude from one side of a triangle as {{mvar|h{{sub|a}}}}, the other two sides as {{mvar|b}} and {{mvar|c}}, and the triangle's [[circumradius]] (radius of the triangle's circumscribed circle) as {{mvar|R}}, the altitude is given by<ref>{{harvnb|Johnson|2007|loc=p. 71, Section 101a}}</ref>

:<math>h_a=\frac{bc}{2R}.</math>