Найдите tg x, если sin x = 0.8, п/2 < x

Так как  п/2< x< п,следовательно это 2-ая четверть и tg в ней отрицательный sin x=0,8=8/10=4/5 sin^2x+co2^2x=1 cos^2x=1-sin^2x cos^2=1-16/25 cos^2x=9/25 cos x=3/5=0,6 4/5: 3/5=4/3 ответ: -4/3

X∈ii

X^2 -9x+11=0;                       x1+x2=9;   x1 *x2=11 (x1)^2+(x2) (x1+x2)^2=(x1)^2 +2*x1 x2 +(x2)^2=((x1)^2 +(x2)^2) +2x1 *x2; x1 *x2=11;               x1)^2 +(x2)^2=(x1+x2)^2 -2x1 *x2                                 (x1+x2)^2=(9^2 -2*11)=81-22=59                   

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