sin cos tan 問題

cosX * sin70° - sinX * sin20° = 1.25 cos70°cosX * cos20° - sinX * sin20° = 1.25 cos70°cos (X + 20°) = 1.25 cos70°X + 20° = 2k(180°) ± arccos (1.25 cos70°) , where k is an integer.X = 360°k ± arccos (1.25 cos70°) - 20°X = 360°k ± 64.6894° - 20°X = 360°k ± 44.6894°

2011-04-27 22:56:12 補充：
修正 :

X = 360°k ± 64.6894° - 20°

X = 360°k + 64.6894° - 20° = 360°k + 44.6894°

或

X = 360°k - 64.6894° - 20° = 360°k - 84.6894°

Sorry!

2011-04-27 22:57:27 補充：
修正 :

X = 360°k ± 64.6894° - 20°

X = 360°k + 64.6894° - 20° = 360°k + 44.6894°

或

X = 360°k - 64.6894° - 20° = 360°k - 84.6894°

Sorry!

2011-04-28 20:19:50 補充：
公式 :

cos(A+B) = cosA cosB - sinA sinB

所以

cos(X+20°) = cosX cos20° - sinX sin20°