prove that:(b+c)cosA+(c+a)cosB+(a+b)cosC=a+b+c?

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prove that:(b+c)cosA+(c+a)cosB+(a+b)cosC=a+b+c?

#put ur mouz pontr on the ques. to see full ques.

2006-11-04 17:23:39 · 4 answers · asked by frank castle 1 in Science & Mathematics ➔ Mathematics

4 answers

we know

a = b cos C + c cos B
b= a cos C + c cos A
c= b cos A + a cos B
adding the 3 and combining cos terms together we get
a+b+c = (a+b) cos C + (b+c) cos A + (c+a) cos B

proved

2006-11-04 19:33:29 · answer #1 · answered by Mein Hoon Na 7 · 1⤊ 0⤋

Eliminate the redundancies and it's evident.

2006-11-05 01:26:40 · answer #2 · answered by Old Cripple 3 · 0⤊ 0⤋

well i cant see the whole prob but im takng algebra right not and pretend you are working with numbers not letters..

2006-11-05 01:26:17 · answer #3 · answered by Anonymous · 0⤊ 0⤋

2006-11-05 01:25:02 · answer #4 · answered by Talamascaa 4 · 0⤊ 0⤋