Question

Sin54градусовsin18градусов

Answer 1

$sin54 times sin18 = frac{sin54 times sin18 times 2cos18}{2cos18} = frac{sin54 times sin36}{2cos18} = frac{sin(90 - 36) times sin36}{2cos18} = \ \ = frac{cos36 times sin36}{2cos18} = frac{0.5sin72}{2cos18} = frac{0.5sin(90 - 18)}{2cos18} = frac{0.5cos18}{2cos18} = \ \ = frac{0.5}{2} = 0.25$
Ответ: 0.25