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tAn255度的三角函数值

250=180+70255=180+7570小于75所以cos250大于cos255

sin255° =sin(180°+75°) = -sin75° = -sin(30°+45°) = -sin30°cos45°-cos30°cos45° = -(1/2)*(√2/2)-(√3/2)*(√2/2) = -(√6+√2)/4 .

tan265°=tan(265-180)°=tan85°=11.430052302761343067210855549163

负1

①sin(-600°)=sin(-720°+120°)=sin120°=32>0;②cos(-710°)=cos(-720°+10°)=cos10°>0;③tan255°=tan(180°+75°)=tan75°>0;④sin420°cos570°=sin(360°+60°)cos(720°-150°)=sin60

tan245=tan(180+45)=-tan45=-1

sin(A+180)=-sinA ∴sin225=sin(45+180)=-sin45=-(根号2)/2 cos(A+180)=-cosA ∴cos225=cos(45+180)=-cos45=-(根号2)/2 tan(A+180)=tanA ∴tan225=tan(45+180)=tan45=1

正弦函数在区间(90°,270°)单调减 sin250° >sin255°

=TAN240=TAN60=根号3

tan225°=tan(180°+45°)=tan45°=1.

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