Сумма равна 29ввввввввввввввввввввввввввввв
sqrt(x) - квадратный корень из x
cos(a)=0.6, 0<a<90,
sin(a)=sqrt(1-cos^2(a))=sqrt(1-0.6*0.6)=sqrt(1-0.36)=sqrt(0.64) = +-0.8, т.к. 0<a<90, значит sin(a) >0, sin(a) =0.8
sin(a+30) = sin(a)*cos(30)+sin(30)*cos(a)=0.8*sqrt(3)/2+1/2 * 0.6=0.4*sqrt(3)+0.3
Ответ 0.4sqrt(3)+0.3
![sin(3x)*cos(x)=sin(2,5x)*cos(1,5x);\\ 0.5*(sin(3x-x)+sin(3x+x))=0.5*(sin(2.5x-1.5x)+sin(2.5x+1.5x));\\ sin(3x-x)+sin(3x+x)=sin(2.5x-1.5x)+sin(2.5x+1.5x);\\ sin (2x)+sin(4x)=sin x+sin (4x);\\ sin(2x)=sin x;\\ sin (2x)-sin x=0;\\ 2sin x cos x-sin x=0;\\ sin x(2cos x-1)=0;](https://tex.z-dn.net/?f=sin%283x%29%2Acos%28x%29%3Dsin%282%2C5x%29%2Acos%281%2C5x%29%3B%5C%5C+0.5%2A%28sin%283x-x%29%2Bsin%283x%2Bx%29%29%3D0.5%2A%28sin%282.5x-1.5x%29%2Bsin%282.5x%2B1.5x%29%29%3B%5C%5C+sin%283x-x%29%2Bsin%283x%2Bx%29%3Dsin%282.5x-1.5x%29%2Bsin%282.5x%2B1.5x%29%3B%5C%5C+sin+%282x%29%2Bsin%284x%29%3Dsin+x%2Bsin+%284x%29%3B%5C%5C+sin%282x%29%3Dsin+x%3B%5C%5C+sin+%282x%29-sin+x%3D0%3B%5C%5C+2sin+x+cos+x-sin+x%3D0%3B%5C%5C+sin+x%282cos+x-1%29%3D0%3B)
остюда либо
k є Z
либо
n є Z
ответ: <var>
k є Z,
n є Z</var>