Solve cos-15?
回答 (3)
2020-08-21 7:15 pm
Trigonometric identity used:
cos(A - B) = cos(A) cso(B) + sin(A) sin(B)
cos(-15°)
= cos(30° - 45°)
= cos(30°) cos(45°) + sin(30°) sin(45°)
= (√3/2) × (√2/2) + (1/2) × (√2/2)
= (√6 + √2)/4
cos(A - B) = cos(A) cso(B) + sin(A) sin(B)
cos(-15°)
= cos(30° - 45°)
= cos(30°) cos(45°) + sin(30°) sin(45°)
= (√3/2) × (√2/2) + (1/2) × (√2/2)
= (√6 + √2)/4
2020-08-22 2:16 am
cos((-15)°)
= (1 + sqrt(3))/(2 sqrt(2))
= 0.96592582628906...
= (1 + sqrt(3))/(2 sqrt(2))
= 0.96592582628906...
2020-08-21 7:06 pm
cos (-15) = cos 15 = (√6+√2)/4
收錄日期: 2021-04-24 07:57:23
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20200821104757AA1KwgY