<span>(Cosx+sinx)^2=cos2x</span>
<span>cos^2x +2sinxcosx+sin^2x=cos2x</span>
<span>sin2x+1-cos2x=0</span>
<span>2sinxcosx+sin^2x+cos^2x-cos^2x+sin^2x=0</span>
<span>2sinx(sinx+cosx)=0</span>
<span>sinx=0</span>
<span>x=ПN</span>
<span>sinx=-cosx/ /cosx</span>
<span>tgx=-1</span>
<span>x=-п/4+пN</span>
<span>(х+6)^2-(х-5)(х+5)=79 х²+12х+36-х²+25=79 12х=18 х=1,5</span>