sin30°+1/2(sin45°+cos45°)-sin^2 20°-cos^2 20°

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sin30°+1/2(sin45°+cos45°)-sin^2 20°-cos^2 20°
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sin30°+1/2(sin45°+cos45°)-sin^2 20°-cos^2 20°
sin30°+1/2(sin45°+cos45°)-sin^2 20°-cos^2 20°

sin30°+1/2(sin45°+cos45°)-sin^2 20°-cos^2 20°
sin30°+1/2(sin45°+cos45°)-sin^2 20°-cos^2 20°
=1/2 +(1/2)(√2/2 +√2/2) -(sin²20°+cos²20°)
=1/2 +√2/2 -1
=(√2 -1)/2