Question

O valor de sen 1280º é igual a

a) - sen 20°
b) - cos 10°
c) - cos 30°
d) - sen 10°
e) - sen 30°

alguém ajuda, pfv​

Answer 1

$\Large\boxed{\begin{array}{l}\sf1280|\underline{360}\\\!\!\!\!\sf-\underline{1080}~~3\\\sf~~ 200\\\sf 1280^\circ=3\cdot360^\circ+200^\circ\\\sf sen(1280^\circ)=sen(200^\circ)=-sen(200-180^\circ)\\\sf sen(1280^\circ)=-sen(20^\circ)\\\Huge\boxed{\boxed{\boxed{\boxed{\boxed{\sf\maltese\,alternativa\,a}}}}}\end{array}}$