怎么画简sin^2a·sin^2阝+cos^2a·cos^2阝-1/2cos2a.cos2阝所以麻烦大神们帮我画简一次

sin a+sin 2a +sin 3a +...+sin na怎么求和? sin a+sin 2a +sin 3a +...+sin na怎么求和? sin(π-2a)怎么化简 2sin²A+sin²2A怎么化简? sin阝=1/3,sin(a+阝)=1,求sin(2a+3阝) 【证明】Sin A+sin B=2Sin 22 sin(arccos(2sin(a)))= 已知sin a-cos a=2sin a*cos a,则sin 2a的值怎么求? 怎么画简sin^2a·sin^2阝+cos^2a·cos^2阝-1/2cos2a.cos2阝所以麻烦大神们帮我画简一次 tan^2θ =2tan^2Ф+1 求证 cos2θ +sin^2Ф=0如题.sin^2a/(1-sin^2a)=2sin^2⊙/(1-sin^2⊙)+1sin^2a/(1-sin^2a+sin^2a)=(sin^2⊙+1)/(1-sin^2⊙+sin^2⊙+1)这是怎么来的。 若sin^2a sin^2(-a)化简 (sinA+sinB)(sinA-sinB) = 1/2 sinC^2是怎么化简成为sin(A+B)sin(A-B) = 1/2sin(A+B)^2 证明sin(a+b)sin(a-b)=sin^2 a-sin^2 b, 求证:sin(a+b)sin(a-b)=sin^2a-sin^2b 2sin^2 a·cos^2 a=(1/2)sin^2 a怎么变来的? cos(A+B)cos(A-B)化简的结果是（ ）A.cos^2A-sin^2BB.sin^2A-sin^2BC.cos^2A-cos^2BD.sin^2A-COS^2B怎么作的? 怎么化简sin（2π+a)cos(π-a)cos(π/2-a）cos(7π/2-a)/cos(π-a)sin(3π-a)sin(-π+a)sin(5π/2+π）