Question

Please anyone help me in this question..​

Answer 1

given f(x)=cos(π2)x + cos(-π2)

=π=3.14

= π2=9

9<π<10  = π2=9

-10<π<-9   = 10

=f(x)=cos9x+cos10x

=f(π/2)=cos9(π/2)+cos10(π/2)

=f(π/2)=0 + (-1)

=f(π/2)=-1