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上△=2x3xsin(夾角)
=2x3xsin(360-90-90-∠ABC)
=2x3xsin(180-∠ABC)
=2x3xsin(∠ABC)=△ABC
同理; 左△=△ABC, 右△=△ABC
三個陰影面積=上△+左△+右△
=3△ABC=3(1/2)(2)(3)sin(∠ABC)
=9sin(∠ABC)
當∠ABC=90度時,
有最大值9
=2x3xsin(360-90-90-∠ABC)
=2x3xsin(180-∠ABC)
=2x3xsin(∠ABC)=△ABC
同理; 左△=△ABC, 右△=△ABC
三個陰影面積=上△+左△+右△
=3△ABC=3(1/2)(2)(3)sin(∠ABC)
=9sin(∠ABC)
當∠ABC=90度時,
有最大值9
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