Question #82a86

1 Answer
P dilip_k
Nov 25, 2017

#cos(tan^-1(4/3)+tan^-1(3/7))#

#=cos(tan^-1[(4/3+3/7)/(1-4/3*3/7)])#
#=cos(tan^-1[(37/21)/(3/7)])#

#=cos(tan^-1[37/9])#

#=cos(sec^-1[sqrt((9^2+37^2)/9^2)])#

#=cos(sec^-1[sqrt(1450)/9])#

#=cos(cos^-1[9/sqrt1450])#

#=9/sqrt1450#

Related questions
Impact of this question
243 views around the world
You can reuse this answer
Creative Commons License