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原式=[2(cos10)^2]/(4sin10cos10)-sin10(cos5/sin5-sin5/cos5)
=cos10/(2sin10)-sin10[(cos5)^2-(sin5)^2]/sin5cos5
=cos10/(2sin10)-sin10(2cos10)/sin10
=(cos10-2sin20)/(2sin10)
=[cos10-2cos(30-10)]/(2sin10)
=(cos10-2sin30cos10+2cos30sin10)/(2sin10)
=(根3)/2.
=cos10/(2sin10)-sin10[(cos5)^2-(sin5)^2]/sin5cos5
=cos10/(2sin10)-sin10(2cos10)/sin10
=(cos10-2sin20)/(2sin10)
=[cos10-2cos(30-10)]/(2sin10)
=(cos10-2sin30cos10+2cos30sin10)/(2sin10)
=(根3)/2.
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