Question 927497
Use half-angle formulas to find the exact values.
(a)cos 112°30'=cos112.5˚
{{{cos(112.5)=cos(225/2)
=-sqrt((1+cos(225))/2)=-sqrt(1-sqrt(2)/2)/2=-sqrt((2-sqrt(2))/4))}}}
..
(c) tan 5π/12
{{{tan(5pi/12)
=tan((5pi/6)/2)
=(sin(5pi/6))/(1+cos(5pi/6))=(1/2)/(1-sqrt(3)/2)=1/(2-sqrt(3))}}}