My family consists of four people: my lovely father, mother, elder brother and me.
My father’s name is Vladimir. He had been working as a deputy manager in the mining company, before he was pensioned off. Now he is 62 and takes care of my mother and our household. By the way, he had started cooking really great dishes after he retired, it's his favorite hobby.
My mother’s name is Olga. She is an IT manager in the treasure house. She has been working with computers for as long as I remember. I think she enjoys tinkering with them and making some changes in the software. She is 58, but still looks as if she's 48. Amazing!
My parents are kind but rather strict in educating their children and grandchildren. They always give me and my brother some good advice on how to live and share their life experience with us.
My elder brother works as a lawyer. His name is Denis. Now he lives with his own family in another country and I terribly miss our get-together time. He is quite handsome man with dark brown hair which has just started to go gray. Thank goodness, my sister-in-law is not a jealous woman. He is sincere and reliable. I can rely on him in any difficult situation. Also he is a 2–year–old girl proud father. Her name is Elizabeth, and she behaves like a real queen. She always demands attention of her parents and likes to boss around a little bit.
I can say that we’re a very amiable family. My parents understand us at first glance, and we help each other without further ado.
20°
Объяснение:
Дано (см. рисунок):
ΔАВС - равнобедренный
AD - биссектриса угла А
BD - биссектриса угла В
∠ADB = 100°
Найти: ∠С
Решение.
Так как треугольник ABC равнобедренный, то у него углы при основании равны ∠А=∠В. Биссектриса делит угол пополам, поэтому α=∠А/2 и β=∠В/2. Но ∠А=∠В и поэтому α=β. Значит, треугольник ADB также равнобедренный.
Найдём углы α и β. Сумма внутренних углов треугольника равна 180°: α + β + 100° = 180°. В силу этого α = β = (180-100)/2 = 40°.
Тогда ∠CАВ=∠СВА=2·α=2·40°=80°. Опять используем свойство:
Сумма внутренних углов треугольника равна 180°.
В силу этого ∠CАВ+∠СВА+∠С=180°. Отсюда
∠C=180°-(∠CАВ+∠СВА)=180°-(80°+80°)=180°-160°=20°.
ответ: 20°