1.（cos10°+√3sin10°）/√(1-cos80°)
=2sin(10°+30°)/√（1-（1-2sin^2(40°)
=2sin40°/√2sin40°
=根号2f(x)=根号3cos(2x/5)+sin(2x/5)
=2[根号3cos(2x/5)/2+sin(2x/5)/2]
=2[sin(π/3)cos(2x/5)+cos(π/3)sin(2x/5)]
=2sin(2x/5+π/3)
2.f(x)的周期为2π/(2/5)=5π
sin(2x/5+π/3)的对称轴之间的距离即为f(x)的半周期
f(x)两条对称轴之间的距离是5π/2
3.=2根号3*(sin12/2cos12-根号3/2)/2sin12cos24
=2根号3(sin12cos60-cos12sin60)/2cos12sin12cos24
=2根号3sin(12-60)/2cos12sin12cos24
=2根号3sin48/sin24cos24
=4根号3sin48/sin48
=4根号3.