Mathematics
Senior High
Resolved
cos(90°-20°)cos(90°-50°)がsin20°sin50°になるのはどうしてですか？教えていただきたいです🙇🏻♀️
(1) cos 70° cos40°-sin 20° sin 50°
[解] cos 70° cos40°-sin20° sin 50°
= cos(90° -20°) cos(90° -50°)-sin20° sin50°
= sin 20° sin 50°-sin 20° sin 50° = 0
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ありがとうございます🙇🏻♀️