ответ: 2 см
Объяснение:
Найдём сначала третью сторону ΔАВС по теореме Пифагора
АС² + ВС² = АВ²
АС² = АВ² - ВС²
АС² = 8² - 4²
АС² = 64 - 16
АС² = 48
АС = √48 = 4√3
Высота прямоугольного треугольника, опущенная из вершины прямого угла вычисляется по формуле: h = 
, где а и в - катеты, с - гипотенуза
h = 
= 2
В прямоугольном треугольнике высота, проведенная к гипотенузе, вычисляется следующим образом: h = 
, где х и у - это отрезки, на которые высота делит гипотенузу.
Пусть BD = х см, тогда АD = (8 - х) см.
Значит, СD = 
CD² = BD . AD
(2√3)² = х · ( 8 - х )
х² - 8х + 12= 0
х = 2 или х = 6
Условию задачи удовлетворяет х=2 ( проверяем теорему Пифагора для ΔCBD).
ответ : ВD = 2 см.
Значи
1.danced, opened, took , rained, had , washed, did ,watched ,cleaned ,went, made , was , got ,lived , wrote
2.we didn't go to Moscow last summer.
the children didn't have dinner at 2o'clock yesterday.
they didn't watch film last week/
I didn't get up at 8 o'clock yesterday.
it didn't rain two days ago
Ann didn't live in S.Petersburg last year/
She didn't read an untersting book the day before yesterday.
I didn't my homework after school yesterday.
3.where the children play in the garden yesterday?
did Tom write a latter three days ago&
What father cook dinneh yesterday&
Who mother go to work by bus yesterday?
When we have a bath the day before yesterday?
Why Nick come home in the aafternoon?
What grandmother make tea in the morning?
4.1 We didn't have lunch at 1o'clock yesterday.Did we have lunch at 1o'clock yesterday? where we have lunch at 1 o'clock yesterday? Who have lunch at 1 o'clock yesterday?
4.2 It didn't show last week.Did it show last week? Where it show last week? Who ishow last week?
5/1 I halped the mom yesterday.
5/2 where you live last month?
5/3 Did they wake up at 7 am ?
5/4 We didn't go to school yesterday
5/5Who watch the TV on Sunday ?