Question

高一数学，求解答，非常感谢！

Answer 1

1）tan20+4sin20
=(sin20+4sin20cos20)/cos20
=(sin20+2sin40)/cos20
=[sin20+2sin(60-20)]/cos20
=[sin20+√3cos20-sin20]/cos20
=√3cos20/cos20
=√3
2)[(1+cos20)/2sin20]-sin10(cot5-tan5)
=2(cos10)^2/4sin10*cos10]-sin10(cos5/sin5-sin5/cos5)
=(cos10/2sin10)-{2*sin10*[(cos5)^2-(sin5)^2]/2sin5cos5}
=(cos10/2sin10)-(2*sin10*cos10/sin10)
=(cos10/2sin10)-(sin20/sin10)
=(cos10-2sin20)/sin10
=[cos10-2sin(30-10)]/sin10
=(cos10-cos10+√3sin10)/sin10
=√3sin10/sin10
=√3
3)(tan10-√3)/csc40
=sin40*(tan10-√3)
=sin40*(sin10-√3cos10)/cos10
=2sin40*(1/2sin10-√3/2cos10)/cos10
=2sin40*sin(10-60)/cos10
=-2sin40*sin50/cos10
=-2sin40*cos40/cos10
=-sin80/cos10
=-cos10/cos10
=-1
4)(√3tan12-3)csc12]/[4(cos12)^2-2]
=(√3tan12-3)/sin12[4(cos12)^2-2]
=√3(sin12-√3cos12)/{cos12*sin12[4(cos12)^2-2]}
=2√3(1/2sin12-√3/2cos12)/{cos12*sin12[4(cos12)^2-2]}
=2√3sin(12-60)/{2cos12*sin12[2(cos12)^2-1]}
=-2√3sin48/sin24*cos24
=-4√3sin48/2sin24*cos24
=-4√3sin48/sin48
=-4√3

Answer 2

迷信迷信迷信迷信迷信