Предмет: Геометрия, автор: ineka1

ПОМОГИТЕ РЕШИТЬ!! НУЖНО СРОЧНО!!!!
№1. В равнобедренном угле DEF (DE=EF)внешний угол при вершине E 144°. Найти все углы треугольника DEF.

№2. Один из внутренних углов, полученных при пересечении 2-х паралельных секущей, в 4 раза больше 2-го. Найти эти углы.

№4. Найдите углы треугольника, если они пропорциональны числам 2,3 и 7.

Ответы

Автор ответа: Аноним
0
№1
Угол Е=180°-144°=36°
Угол D=углу  F= (180°-36°):2=72°Так как углы при основании равны
Ответ: 72°;72°;36°
№2
Это могут быть только односторонние углы, их сумма равна 180°
Пусть меньший угол х, тогда больший 4х
Решим уравнение 
х+4х=180
5х=180
х=36°- это меньший угол 
36·4=144°- это больший угол 
Ответ: 144° и 36°
№4
Решим уравнение 
2х+3х+7х=180  ( обозначив одну часть за х)
12х=180
х=180:12
х=15 - это 1 часть
2·15=30°
3·15=45°
7·15=105°
Ответ: 30°;45°;105°
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