if cosA=cosB.cosC,then prove tanA=tanB.tanC and A+B+C=180
Answers
Answered by
1
Answer:
cos a = - cos(b+c) = - (cos b cos c - sin b sin c) = - cos b cos c + sin b sin c
But cos a =cos b cos c so
- cos b cos c + sin b sin c = cos b cos c and therefore
sin b sin c = 2 cos b cos c
Dividing through by cos b cos c we get
tan b tan c = 2 q.e.d
Step-by-step explanation:
Similar questions