Question

奶油真好吃

Cos跟sin皆負的不就是在第三象限嗎？？
為什麼不是210而是150？？？？？

7.200
-57030
-:= 25πn (X-210°)
ⅱ)+3
25TH
=25in (x-150°)

Answer 1

✨ Jawaban Terbaik ✨

qn

sinx · (-√3/2) + cosx · (-1/2)
= sinx cos210° + cosx sin210°
= sin(x+210°)
= sin(x-150°)

或是

sinx · (-√3/2) - cosx · (1/2)
= sinx cos150° - cosx sin150°
= sin(x-150°)