Question

$if \: a+ b+c=180\:then\:Σ\frac{ \cot\:a + \: \cot \: b }{ \tan \: a + \tan \: b } =$
please answer this question​

Answer 1

Answer:

applying cos on both sides

cos (A+B+C)=cos(180)

cot A cotB cotC+cotB cotA-1/cotA+cotB+cotC-cotA cotB cotC =1/2

cot(A+B+C)=cot A cotB+cotC +cotB cotA-1/cotA+cotB+cotC-cotA cotB cotC

cotA+cotB+cotC- cotA cotB cotC=0

cotA+cotB+cotC=cotA cotB cotC

cotA+cotB+cotC/cotA cot B cot C=1