Cos(a+β)+sina*sinβ=cosa*cosβ-sina*sinβ+sina*sinβ=cosa*cosβ
cosa=-2/5
cosβ=15/16
cosa*cosβ=-2/5*15/16=-3/8
Ответ: -3/8
(2сosx-1)(3sinx-4)=0
[2cosx-1=0
[3sinx-4=0
[cosx=1/2
[ sinx=4/3
[x=+-arccos(1/2)+2пk
[ x=нет корней
x=+-п/3 + 2пk, k<span>∈Z</span>
<span>3^x^2 + 108=5^1-x^2 * 15^x^2
3^(x^2) + 4*3^3 = 5^(1-x^2) * 3^(x^2)*5^(x^2)
</span>3^(x^2) + 4*3^3 = 5^(1-x^2 +x^2) * 3^(x^2)
3^(x^2) + 4*3^3 = 5 * 3^(x^2)
4*3^3 = 4 * 3^(x^2)
3^3 = 3^(x^2)
3= x^2
x = +-√3
произведение корней √3 * (-√3) = -3