sin(-19π/6)/(sec4π/3)+tan7π/4=详细过程谢谢这是道选择题A1/6B-1/6C√3/3D-√3/3

sin(-19π/6)/(sec4π/3)+tan7π/4= sin(-19π/6)/(sec4π/3)+tan7π/4=详细过程谢谢这是道选择题A1/6B-1/6C√3/3D-√3/3 sin（-19π/6）/sec4π/3-tan7π/4=a、b为锐角,且cosa=5/13,sinb=4/5,则cos（a+b）=y=3sin(4x+π/3）最小正周期是?在△ABC中.若边a:b:c=根号2：（1+根号3）：2,则内角A=? 已知α=π/24,求sinα(sec4αsec3α+sec3αsec2α+sec2αsecα+secα)=?求具体化简过程 sin（-19π/6）=?已知[3Sin(π+a)+Cos(π-a)]/4Sin(-a)-Sin(5π/2+a)=2，求tan a Sin(π+π/6)Sin(2π+π/6)Sin(3π+π/6).Sin(2008π+π/6)求值 sin^2(π/3-x)+sin^2(π/6+x) 2sin π/6 =sin π/3,吗,求解释,还有-sin π/6=sin- π/6吗 [Sin(6π+a)Cos(7π-a)]/[Sin(3π+a)+Sin(-π+a) 关于三角函数的的两个题目的解答（请求给出过程）1.证明1+3·sin2α·sec2α+tan6α=sec6α2.证明(sinα+secα)的3次幂+（cosα+cscα）的2次幂=(1+secαcscα)2次幂改正为下1+3·sin2α·sec4α+tan6α=sec6α sin 11π/6 sin(-π/3) 计算,sin(π/12)-sin(5π/12)+2sin(π/8)sin(3π/8) 化简sin(α+β)+sin(α-β)+2sinαsin(3π/2-β)= 已知sin（X+π/6）=2/3,求sin（X+19π/6）+sin²（π/3-X）的值? 已知sin（X+π/6）=2/3,求sin（X+19π/6）+sin²（π/3-X）的值? [sin(a-6π)cos(7π/2-a)]/[sin(3π+a)+sin(a-π）】= sin(-19/6π)的值等于?