2sin (65°-x/4)-1=0 Sin2x=0

Đáp án:

2sin (65°-x/4)-1=0

<=> sin(65°-x/4)=1/2;

<=> sin(65°-x/4)=sin 30°;

<=> $\left \{ {{(65°-x/4)=30°+k360°} \atop { (65°-x/4)=180°-30°+k360°}} \right.$ ;

<=>$\left \{ {{(65°-x/4)=30°+k360°} \atop { (65°-x/4)=150°+k360°}} \right.$ ;

<=>$\left \{ {{x=140°-k1440°} \atop { y=-340°-k1440°}} \right.$ ;

b) sin2x=0; <=> sin2x=sin 0;

<=> 2x=k$\pi$ ;

<=> x=k$\pi$ /2

Giải thích các bước giải:

Đáp án:

1/<=> 2sin (pi/3 - x/4) =1

<=> sin (pi/3 - x/4) = 1/2

<=> sin (pi/3 - x/4) = sin (pi/6)

<=> pi/3 - x/4 = pi/6 + k2pi

pi/3 -x/4 = 5pi/6 +k2pi

<=> x/4 = - pi/6 + k2pi

x/4 = pi/2 +k2pi

<=> x= -2pi/3 + kpi/8

x= 2pi + kpi/8

2/ sin2x=0

<=> 2x = kpi

<=> x= kpi/2