How do you evaluate #cos ((7 pi)/3 + (15 pi)/4)#?

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Answer 1 · 2016-06-04T16:57:04

#=(sqrt 3+1)/(2 sqrt 2)#

#cos ((7pi)/3+(15pi)/4)#

#=cos (2pi+pi/3 + 4pi-pi/4)#

#=cos(6pi+(pi/3--pi/4))#

#=cos (pi/3-pi/4)#

#=cos(pi/3)cos(pi/4)+sin(pi/3)sin(pi/4)#

#=(1/2)(1/sqrt 2)+(sqrt 3/2)(1/sqrt 2)#

#=(sqrt 3+1)/(2 sqrt 2)#