cos(45+30)cos(45-30)+sin(45+30)sin(45-30)
=cos[(45+30)-(45-30)]
=cos(75-15)
=cos60
=1/2
cos(45+30)cos(45-30)+sin(45+30)sin(45-30=)
2个回答
相关问题
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为什么sin(45-30)=sin45*cos30-sin30*cos45?
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（cos 45°-sin 30°）/（cos 45°+sin 30°）
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1.cos30°-sin45°/sin60°-cos45° 2.(sin30^2)30°+2sin60°+tha45°-
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cos30°,45°60° tan60°45°30° sin30°60°45°
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cos30°— sin45° ———————— sin60°— cos45°计算
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cos sin tancos30' 45' 60' sin 30' 45' 60' tan 30' 45' 60' 各等
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sin30° sin45° sin60° cos30° cos45° cos60° 以此类推,都等于多少
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（1）cos60°-sin^2 45°+sin^2 45°+1/4tan^2 30°+cos30°-sin30°
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超简单的三角函数,忘记了tan30·tan45· tan60·sin30·sin45·sin60·cos30·cos45
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(1+Cos45°-Sin30°)(1-Sin45°+Cos60°)=