Question 861386
{{{cos(2*theta)+cos(theta)=0}}}
{{{cos^2(theta)-sin^2(theta)+cos(theta)=0}}}
{{{cos^2(theta)-sin^2(theta)+cos(theta)=0}}}
{{{cos^2(theta)-(1-cos^2(theta))+cos(theta)=0}}}
{{{cos^2(theta)-1+cos^2(theta)+cos(theta)=0}}}
{{{2cos^2(theta)+cos(theta)-1=0}}}
Let {{{u=cos(theta)}}}
{{{2u^2+u-1=0}}}
{{{(u+1)(2u-1)=0}}}
Two solutions:
{{{u+1=0}}}
{{{u=-1}}}
{{{cos(theta)=-1}}}
{{{theta=pi}}}
Not in the solution region.
{{{2u-1=0}}}
{{{2u=1}}}
{{{u=1/2}}}
{{{cos(theta)=1/2}}}
{{{theta=pi/3}}} and {{{theta=(5/3)pi}}}
Only {{{theta=pi/3}}} is in the solution region.
{{{theta=pi/3=60}}}{{{degrees}}}