求证3-sin^4a-cos^4a/2cos^a=1+tan^a+sin^a 速答 谢谢

求证3-sin^4a-cos^4a/2cos^a=1+tan^a+sin^a 速答 谢谢 三角函数 求证:cos^2(a)-cos(2a)*cos(4a)=sin^2(3a)求证:cos^2(a)-cos(2a)*cos(4a)=sin^2(3a) 求证1/sin^2a+3/cos^2a>=4+2根号下31/sin²a +3/cos²a=(sin²a+cos²a)/sin²a +3(sin²a+cos²a)/cos²a=1+cos²a/sin²a+3+3sin²a/cos²a=4+cos²a/sin²a+3sin²a/cos²a≥4+2√[(cos 求证sin^2a+cos^2(a+30°)+sinacos(a+30°)=3/4 求证2cos^2a+sin^4a=cos^4a+1 求证：sin²A+cos²（A+30）+sinA*cos(A+30)=3/4 求证sin^4a+cos^4a=1-2sin^2acos^2a 求证sin^4a-cos^4a=-cos2a如题 求证 sin^4(a)-cos^4(a)=-cos(2a) sin∨4a-cos∨4a=sin²a-cos²a 求证 高一向量问题.已知向量a=(cosα,sinα),向量b=（cosβ,sinβ）,向量c=（cosγ,sinγ）已知向量a=(cosα,sinα),向量b=（cosβ,sinβ）,向量c=（cosγ,sinγ）且3cosα+4cosβ+5cosγ=0, 3sinα+4sinβ+5sinγ=0.（1）求证向量a 设A(cosa,sina)、B(cos(2派/3 +a),sin(2派/3 +a))、C(cos(4派/3 +a),sin(4派/3 +a)),求证向量OA+OB+OC=0. 求证sin^4a=1/8(3－4cos^2a+cos4a) 求证 sin~4a-cos~4a=sin~2a-cos~2a tan~2asin~2a=tan~2a-sin~2a 三角形ABC,求证cos(A+B)=-cosC,cos[(A+B)/2]=sin(C/2)和sin(3A+3B)=sin(3C),sin[(3A+3B)/2]=-cos[(3C)/2] 求证sin^4a+cos^4a=1 求证：cos^2a-cos2acos4a=sin^2 3a 求证:cos^2a-cos2acos4a=sin^2 3a 求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a