Вычислите 1) cos 75= в радианах 2) sin 67 sin 7+cos 67 cos7 3)sin 87 cos3+ cos87 sin 3

b1+b2=-10

b2+b3=-5

b1+b1q=-10

b1q+b1q^2=-5

b1(1+q)=-10

b1q(1+q)=-5

b1=-10/(1+q)

-10q(1+q)/(1+q)=-5

b1=-10/(1+q)

-10q=-5

b1=-10/(1+q)

q=1/2

b1=-10(1+1/2)

q=1/2

b1=-20/3

q=1/2

b2=b1q=-20/3*1/2=-10/3

b3=b2q=-10/3*1/2=-5/3

-20/3; -10/3; -5/3