Question

ГДЗ по Геометрии за 7‐9 класс задачи на готовых чертежах для подготовки к ОГЭ и ЕГЭ Балаян Э.Н. 2018
Нужно 2 и 4​

Answer 1

Given :  Triangle

To Find " Value of x

Solution:

Cosine formula for triangle :

c² = a² + b²  - 2abcosC

x² = 18² + 16² - 2(18)(16)Cos130°

=> x² = 324 + 256 + 370.246

=> x = 30.826

x² =5² + √8² - 2(5)(√8)Cos45°

=> x² = 25 + 8  - 20

=> x² = 13

=>  x=  √13

4² = 10² + 7² - 2(10)(7) cosx

=> 16 = 149 - 140Cosx

=> Cosx = 133/140

=> Cosx = 0.95

=>  x= 18.195°

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