sin=3/5,Sin(a+阝)=5/13(a,a+阝都为第一象限角),求Cos阝的值.

sin阝=1/3,sin(a+阝)=1,求sin(2a+3阝) 已知3SIN^2A+2SIN^2B=5SINA,求SIN^2A+SIN^2B范围 sin(a+b)=1/3,sin(a-b)=1/5,则tana*cotb=? 已知sin(a+b)等于2/3,sin(a-b0 =1/5,求tana:tanb 已知sin a+cos a= -1/5 求1）sin acos a 2）sin a-cos a 化简sin(4π-a)*sin(5π-a)=? 已知tan a =-4,求下列各式的值 (1)sin^2 a (2)3sin acos a (3)cos^2 a-sin^2 a (4)4sin a已知tan a =-4,求下列各式的值 (1)sin^2 a (2)3sin acos a (3)cos^2 a-sin^2 a (4) (4sin a-2cos a)/(5cos a+3sin a) a为任意角 已知tan a =-4,求下列各式的值 (1)sin^2 a (2)3sin acos a (3)cos^2 a-sin^2 a (4)4sin a已知tan a =-4,求下列各式的值 (1)sin^2 a (2)3sin acos a (3)cos^2 a-sin^2 a (4) (4sin a-2cos a)/(5cos a+3sin a) a为任意角 sin（-19π/6）=?已知[3Sin(π+a)+Cos(π-a)]/4Sin(-a)-Sin(5π/2+a)=2，求tan a 已知：1/2sin a +根号3/2cons a=3/5 sin^2a+cos^2a=1 求sin a sin2a=3/5,求sin a. sin(α+β)=2/3,sin(α-β)=3/5,sinα+sinβ=1/2,求cos(α+β)/2*sin(α-β)/2 s = 2*sin(x)-sin(2*x)+2/3*sin(3*x)-1/2*sin(4*x)+2/5*sin(5*x)用matlab画图,求教啊 已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a= tan a =3求4sin a-2cos a/5cos+3sin a sin(2π+a) ,sin(π+a),sin(5π+a) 的区别为什么sin(2π+a) =sina sin(π+a)=-sina 1-1/4sin^2 2A-sin^2B-cos^4Asin(A+B)=3/5sin(A-B)=-4/5 1-sin a+sin a的平方-sin a的立方+……若a是正锐角,且sin a-cos a=0.5,求1-sin a+sin^2a-sin^3a+……