Question 928626


{{{ tan(t)=12/5 }}} and {{{ pi<t<3pi/2 }}}

{{{ tan^-1(12/5)= 1.176}}} in radians

or

{{{ tan^-1(12/5)= 67.38°}}}

then {{{cos(t/2)=cos(1.176/2)= cos(0.588)=0.83205}}}

or

{{{cos(t/2)=cos(67.38/2)= cos(33.69)=0.83205}}}

your choices are:

a) {{{2sqrt(13)/13=0.5547}}}.........excluded 
b) {{{highlight(3sqrt(13)/13=0.83205)}}}.......your answer..
c) {{{-3/-2=1.5}}}.................excluded 
d) {{{-7sqrt(13)/-13=1.94145}}}.................excluded