2*sin55*cos55*(cos55/sin55)-1=
2(cos55)^2-1=
2(cos55)^2 - (cos55) ^2-(sin55)^2 =
(cos55) ^2-(sin55)^2=cos110
25-x^2=5^2-x^2=(5-x)(5+x)
A₁₀=13
a₅=18
a₁₀=a₁+9d, a₅=a₁+4d
a₅-a₁₀=18-13
a₁+4d-a₁-9d=5
-5d=5
d=-1
(3*корень_из_5)^2 = 3^2 * 5 = 45
<span>Решение на фото............................................................................</span>