Question

Помогите пожалуйста

Answer 1

Ответ:

Объяснение:

По теореме косинусов

3.5²=5.6²+5.8²-2*5.6*5.8*cos∡F

12.25=31.36+33.64-64.96 *cos∡F

64.96 *cos∡F =52.75

cos∡F≈0.81

∡F≈35.7°

sin²∡F=1-cos²∡F =1-0.81²=0.3439

sin∡F≈0.59

=>S(ΔDEF)= 0.5*5.8*5.6*0.59 ≈9.58

По теореме синусов

3.5/sin∡F= 5.6/sin∡D => 3.5/0.59 =5.6/sin∡D

sin∡D =5.6*0.59/3.5=0.944

=> ∡D≈70.7°

∡E=180°-∡F-∡D=180°-35.7°-70.7°=73.6°