Name: Bryant
Who is asking: Other
Question: c^{ 2} = a^{ 2} + b^{ 2}  2ab cos C cos(180 degrees  C) = cos C Hi,
In the diagram below of a triangle with angle C obtuse, I extended the line segment BC drew a perpendicular from A to meet this extended line at D. Let x be the length of CD and h the length of AD. Triangle ABD is a right triangle and hence = (a + x)^{ 2} + h^{ 2} = a^{ 2} + 2ax + x^{ 2} + h^{ 2} = a^{ 2} + b^{ 2} +2ax Can you complete the proof? Penny
