Question 768931


since {{{cos(x-(3pi/2)) = -sin(x) }}}, we have

{{{cos(x-(3pi/2)) +cos(x-(3pi/2)) = -2 sin(x)}}}


 and {{{-2 sin(x)= 0}}} for all {{{x = pi* n}}}, where {{{ n}}} element {{{Z}}}

since {{{sin(pi)=0}}} we can use any number {{{n}}}, result will be {{{0}}}
for example if {{{n=1}}}, then {{{sin(pi) = 0}}}, as {{{sin(2pi)=0}}} as well, and so on