150 баллов! Тригонометрия

Question

150 баллов! Тригонометрия

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Answer 1

Sin^2x+2cos^x=sin^2x+cos^2x+cos^2x=1+cos^2x
0<=cos^2x<=1<br>1<=1+COS^2X<=2<br>1+2=3
3cos^2x-4sin^2x=3cos^2x-3sin^2x-sin^2x=3cos2x-sin^2x
-1<=-sin^2x<=0<br>-3<=3cos2x<=3<br>-4<=3cos2x-sin^2x<=3<br>-4+3=-1