Question 337025
Use a substitution,
{{{u=cos(x)}}}
{{{2u^2-3u-2=0}}}
{{{(2u+1)(u-2)=0}}}
Two solutions:
{{{2u+1=0}}}
{{{2u=-1}}}
{{{u=-1/2}}}
{{{cos(x)=-1/2}}}
{{{x=(2*pi)/3}}}, {{{(4*pi)/3}}}
.
.
.
{{{u-2=0}}}
{{{u=2}}}
{{{cos(x)=2}}}
No solutions.