Nilai dari cos 40+ cos 80+ cos 160 =...

Halo, Adik. Kakak bantu jawab ya :) Jawabannya adalah 0. INGAT! cos A + cos B = 2 cos((A+B)/2) cos((A-B)/2) cos(180° - A) = - cos A cos(-A) = cos A Perhatikan penjelasan berikut. cos40° + cos80° + cos160° = (cos40° + cos80°) + cos(180°-20°) = (2 cos((40°+80°)/2) cos((40°-80°)/2)) + (- cos20°) = (2 cos(120°/2) cos(-40°/2)) - cos20° = (2 cos60° cos(-20°)) - cos20° = (2 cos60° cos20°) - cos20° = (2∙½∙cos20°) - cos20° = cos20° - cos20° = 0 Jadi, nilai dari cos40° + cos80° + cos160° = 0. Semoga membantu ya :)