Question 155226
{{{cos(2u)=cos^2(u)}}}
By double -Angle Formula:
{{{cos(2u)=2cos^2(u)-1}}}
So,
{{{2cos^2(u)-1=cos^2(u)}}}
{{{2cos^2(u)-cos^2(u)=1}}}
{{{cos^2(u)(2-1)=1}}}
{{{cos^2(u)=1}}}
{{{cos^2(u)-1=0}}}
By Pythagorean Identities:
{{{sin^2(u)+cos^2(u)=1}}}
{{{sin^2(u)=1-cos^2(u)}}}
Therefore,
{{{cos^2(u)-1}}} -----------> {{{-sin^2(u)}}}
Thank you,
Jojo