[中學] 一題三角極值

[hero010188 (我是海賊王)]

https://i.imgur.com/G6WKfIK.jpg
怎麼處理較好@@"

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→ pnicarevol  : f(x) = 2sin(2x+30°) + 2sin(x-30°)
→ pnicarevol  :      = 2[sin(2y+90°)+sin(y)]  (let y = x-30°)
→ pnicarevol  :      = 2[cos(2y)+sin(y)]
→ pnicarevol  :      = 2[1-2sin^2(y)+sin(y)]
→ pnicarevol  : 當sin(y)=1/4時有極大值9/4
→ hero010188  : 謝! 厲害!