Question

1. cos^2x+3sin^2x+2корень из 3 sinxcosx=1 2. sinx+sin3x=sin5x+sinx 3. sinxcosx+cos^2 x=0 4. 2cos^2x+5cosx+2=0

Answer 1

$1. cos^2+3sin^2+2\sqrt3sinx*cosx=1;\\ cos^2x+3sin^x+2\sqrt3sinx*cosx-sin^2x-cos^x=0;\\ 2sin^2x+2\sqrt3sinx*cosx=0\ |:cosx;\\ 2tg^2x+2\sqrt3tgx=0;\\ 2tgx(tgx+\sqrt3)=0;\\ 2tgx=0;\ \ \ x=\pi*n;\\ tgx+\sqrt3=0;\\ tgx=-\sqrt3; \ \ \ x=-\frac{\pi}{3}+2*\pi*n;\\ \\ \\$

$3. sinx*cosx+cos^2x=0 \ |:cos^2x;\\ tgx+1=0;\\ tg=-1;\ \ \ x=-\frac{\pi}{4}+\pi*n.\\ \\ \\ 4.\\ 2cos^x+5cosx+2=0\ \ \ cosx=t,\ \ \ |t|\leq1;\\ 2t^2+5t+2=0;\\ D=25-16=9;\\ t_1=\frac{-5+3}{4}=-\frac{1}{2};\\ t_2=\frac{-5-3}{4}=-2 - lishnii;\\ cosx=-\frac{1}{2};\ \ \ x=+-\pi-\frac{\pi}{3}+2\pi*n$