3а+5-2+а=4а+3. Элементарно
=Cosxcosy-sinxsiny=0
0,6*cosy-0,8siny=o
7х-2=4
7х=4+2
7х=6
х=6/7
*в дес. дробях: 0,857142857143
Sin( (5/6)*(π(6x+1)) =cos((1/3)*(π(3x+2)) ; x∈(0; 1/2).
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sin( π*( (5/6)*6x +(5/6)*1) ) =cos( π*((1/3)*3x+(1/3)*2) ) ;
sin( π(5x +5/6)) =cos( π(x+ 2/3) ) ;
sin( π(5x +5/6)) =sin( π/2- π(x+ 2/3) ) ;
sin( π(5x +5/6)) = sin( π(1/2- x- 2/3) <span>) ;
</span>sin( π(5x +5/6)) = sin(- π(x+1/6) ) ;
sin( π(5x +5/6)) + sin( π(x +1/6) <span>) =0 ;
</span>2sin( π(3x +1/2))*cos( π<span>(2x+1/3)) =0 ;
[ </span>sin π(3x +1/2)) =0 ; cos( π<span>(2x+1/3) )=0 </span> .
а)
π(3x +1/2) =πn ,n∈Z.
3x +1/2 = n ⇒x = -1/6 +n/3 ,если n =1⇒ x =1/6 ∈ (0; 1/2) .
<span>* * * 0< -1/6 +n/3 < 1/2</span>⇔ 1/6<n/3< 1/6+1/2 ⇔1/2<n<2 ⇒n=1* * *
б)
π(2x+1/3) = π/2 +πn ,n∈Z.
2x+1/3 = 1/2 +n ⇒ x =1/12+ n/2,если n =0⇒ x =1/12 <span>∈ (0; 1/2)</span>.
* * * 0< 1/12 +n/2 < 1/2⇔ - 1/12 <n/2< -1/12+1/2 ⇔-1/6<n<5/6 ⇒n=0* * *
<span>
сумма корней будет: (1/6 +1/12) =1/4.
ответ : </span>1/4 .