Question

if ABCD is a triangle the cosA+ cosB+cosC + cosD​

Answer 1

Answer:

0

Step-by-step explanation:

bro your question is wrong

is it traingle or quadrilaterial ?

If ABCD is a cyclic quadrilateral taken in order, then A + C = 180° and B + D = 180°  

==> A = (180 - C)  

==> cos(A) = cos(180 - C) = -cos(C)  

==> cos(A) + cos(C) = 0 ------ (1)  

Similarly it can be shown that cos(B) + cos(D) = 0 ----------- (2)  

Adding (1) & (2): cos(A) + cos(B) + cos(C) + cos(D) = 0

hope it helps

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