Сума кутів трикутника завжди дорівнює 180°.
Кути при основі рівні, тому що трикутник рівнобедренний.
180°- 120°= 60° - це залишок на два кути.
60°/2= 30° - кут при основі.
She said she had heard about it before.
Miss Barkley said that I would come with her to see Ann.
He said he didn’t know.
My friend said that he hadn’t joined them in the bar.
My cousin said he couldn’t help me.
His parents said to him that they knew all about it then.
Nick said that he had been working all day the day before.
She said he didn’t know why he had wanted to go to war.
His friend said that he had been leading a sort of an interesting life.
Число 18.решение:702 : 39 = 18
По основному тригонометрическому тождеству:
sin²x+cos²x=1
тогда cos²x=1-sin²x
Уравнение преобразуется в:
sin²(x)-3*sin(x)-1=0
sin(x)=(3+_√5)÷2
Так как √5>0, следовательно, 3+√5>3
но 1,5>1, тогда как sin(x)∈[-1;1]
проверим -:
Предположим
3-√5<2
√5>1
Это так, значит предположение верно.
Ответ: sin(x)=(3-√5)÷2