How do you find critical points for the equation #(7/10)cos(x/10)#?

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Answer 1 · 2018-06-25T05:25:14

#x=10kpi# where #k# is an integer.

#f(x)=7/10cos(x/10)#

Critical points are when derivative is 0 or undefined.

#f'(x)=-7/100sin(x/10)#

Sin is well defined at every point but is equal to zero at 0,#pi#

#-7/100sin(x/10)=0#

#sin(x/10)=0

#sin(y)=0 # at #y=kpi#

Therefore

#sin(x/10)=0# at # x/10=kpi# so #x=10kpi# where #k# in an integer.