Question

Довести що sin 35°+cos65°=cos 5°

Answer 1

Решение во вложении.

Answer 2

$sin(35^{\circ})+cos(65^{\circ})=cos(5^{\circ})\\sin(35^{\circ})+cos(90^{\circ}-25^{\circ})=cos(5^{\circ})\\sin(35^{\circ})+sin(25^{\circ})=cos(5^{\circ})\\2sin(30^{\circ})cos(5^{\circ})=cos(5^{\circ})\\cos(5^{\circ})=cos(5^{\circ})\blacksquare$