化简sin²a+sin²β-sin²asin²β+cos²acos
sin²a+cosˇ4a+sin²acos²a 化简
化简:sin^2a+sin^2β-sin^2asin^2β+cos^2acos^2β
求证sin^4a+cos^4a=1-2sin²acos²a
求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[
2.证明:sin²²a+cos²²a=1-2sin²acos²
sin²α+sin²β—sin²αsin²β+cos²αcos
sin²A+sin²B=cos²C
sin²A+cos²A是多少
cos²a + sin²a=?
化简sin²α-2sinαcosα+1
求证:sin²A+sin²B-sin²A·sin²B+cos²A·co
如果cos²α-cos²β=a 则sin(a+ β)sin(a-β)等于