(cos(80°)-cos(40°))/sin(40°) = ?

1 Answer
Nityananda
Oct 8, 2017

#sqrt 3#

Explanation:

We know, cos C - cos D = - 2 sin(C + D)/2. sin (C - D)/2

Hence,#[ cos 80 - cos 40]/sin 40#

#rArr [ - 2 sin (80+40)/2. sin (80-40)/2]/sin 40#

#rArr [ - 2 sin 60. sin 40]/sin 40#

#rArr - 2 sin 60#

#rArr - 2. sqrt 3 /2 = - sqrt 3#

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