2a向量=(sin2x,cos2x),b=(cos2x,-cos2x)2、a向量=(根号3sin2x,cos2x),b=(cos2x,-cos2x)(1) x∈(7/24∏,5/12∏),a*b+1/2=-3/5,求cos4x(2) 三角形ABC的三边分别是a,b,c,且b*b=ac,b边对应的角为x,a向量*b向量+1/2有且仅有一
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![2a向量=(sin2x,cos2x),b=(cos2x,-cos2x)2、a向量=(根号3sin2x,cos2x),b=(cos2x,-cos2x)(1) x∈(7/24∏,5/12∏),a*b+1/2=-3/5,求cos4x(2) 三角形ABC的三边分别是a,b,c,且b*b=ac,b边对应的角为x,a向量*b向量+1/2有且仅有一](/uploads/image/z/10130642-26-2.jpg?t=2a%E5%90%91%E9%87%8F%3D%EF%BC%88sin2x%2Ccos2x%EF%BC%89%2Cb%3D%28cos2x%2C-cos2x%292%E3%80%81a%E5%90%91%E9%87%8F%3D%EF%BC%88%E6%A0%B9%E5%8F%B73sin2x%2Ccos2x%EF%BC%89%2Cb%3D%28cos2x%2C-cos2x%29%281%29+x%E2%88%88%287%2F24%E2%88%8F%2C5%2F12%E2%88%8F%29%2Ca%2Ab%2B1%2F2%3D-3%2F5%2C%E6%B1%82cos4x%282%29+%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E7%9A%84%E4%B8%89%E8%BE%B9%E5%88%86%E5%88%AB%E6%98%AFa%2Cb%2Cc%2C%E4%B8%94b%2Ab%3Dac%2Cb%E8%BE%B9%E5%AF%B9%E5%BA%94%E7%9A%84%E8%A7%92%E4%B8%BAx%2Ca%E5%90%91%E9%87%8F%2Ab%E5%90%91%E9%87%8F%2B1%2F2%E6%9C%89%E4%B8%94%E4%BB%85%E6%9C%89%E4%B8%80)
2a向量=(sin2x,cos2x),b=(cos2x,-cos2x)2、a向量=(根号3sin2x,cos2x),b=(cos2x,-cos2x)(1) x∈(7/24∏,5/12∏),a*b+1/2=-3/5,求cos4x(2) 三角形ABC的三边分别是a,b,c,且b*b=ac,b边对应的角为x,a向量*b向量+1/2有且仅有一
2a向量=(sin2x,cos2x),b=(cos2x,-cos2x)
2、a向量=(根号3sin2x,cos2x),b=(cos2x,-cos2x)
(1) x∈(7/24∏,5/12∏),a*b+1/2=-3/5,求cos4x
(2) 三角形ABC的三边分别是a,b,c,且b*b=ac,b边对应的角为x,a向量*b向量+1/2有且仅有一个实数根,求m
2a向量=(sin2x,cos2x),b=(cos2x,-cos2x)2、a向量=(根号3sin2x,cos2x),b=(cos2x,-cos2x)(1) x∈(7/24∏,5/12∏),a*b+1/2=-3/5,求cos4x(2) 三角形ABC的三边分别是a,b,c,且b*b=ac,b边对应的角为x,a向量*b向量+1/2有且仅有一
a*b+1/2=-3/5
√3sin2xcos2x-cos2xcos2x+1/2=-3/5
√3/2sin4x-1/2cos4x=-3/5 (1)
sin(4x-π/6)=-3/5
x∈(7/24∏,5/12∏),
π
a*b=根号3sin2x*cos2x-cos2x*cos2x=cos2x(2sin(2x+π/3)) a*b+1/2=-3/5 a*b=-11/10
cos2x(2sin(2x+π/3)=-11/10 cos^2 x+sin^2 x=1 算出sinx cosx x∈(7/24∏,5/12∏),判断他们的正负然后算cos2x sin2x 最后算出结果
m是什么啊