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tan240°=tan(180°+60°)=tan60°=√3
sec100°+tan240°*csc100°
=1/cos100°+√3/sin100°
=(sin100°+√3cos100°)/sin100°cos100°
=4(sin100°/2+√3cos100°/2)/2sin100°cos100°
=4sin(100°+60°)/sin200°
=4sin(160°)/sin200°
=4sin(360°-200°)/sin200°
=-4sin200°/sin200°
=-4
sec100°+tan240°*csc100°
=1/cos100°+√3/sin100°
=(sin100°+√3cos100°)/sin100°cos100°
=4(sin100°/2+√3cos100°/2)/2sin100°cos100°
=4sin(100°+60°)/sin200°
=4sin(160°)/sin200°
=4sin(360°-200°)/sin200°
=-4sin200°/sin200°
=-4
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