А + Б + В = 180
А + 18 = С
А - 45 = Б
А + 18 + А - 45 + А = 180
3А = 207
А = 69
Б = 24
С = 87
1) cos^2x = 1/2
cosx = - √2/2
x1 = (+ -)arccos(-√2/2) + 2πn, n∈Z
x1 = (+ -)(π - π/4) + 2πn, n∈z
x1 = (+ -)(3π/4) + 2πn, n∈Z
2) cosx = √2/2
x2 = (+ -)arccos(√2/2) + 2πk, n∈Z
x2 = (+ -)(π/4) + 2πk, n∈Z
2) sin^2x = 1
a) sinx = -1
x1 = - π/2 + 2πm, m∈Z
b) sinx = 1
x2 = π/2 + 2πk, k∈Z
11 - 0,2b = 7
- 0,2b = 7 - 11
- 0,2b = - 4
b = - 4 : (- 0,2) = 20
64-(4-3а)(16+12а+9а²)=64-(64-27а³)=27а³