求证(1)sin4平方a+sin²acos²a+cos²a=1(2)tan²a-sin²a=tan²asin²a
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求证(1)sin4平方a+sin²acos²a+cos²a=1(2)tan²a-sin²a=tan²asin²a
求证(1)sin4平方a+sin²acos²a+cos²a=1(2)tan²a-sin²a=tan²asin²a
求证(1)sin4平方a+sin²acos²a+cos²a=1(2)tan²a-sin²a=tan²asin²a
证明∶
(1)
sin⁴a+sin²acos²a+cos²a
=sin²a(sin²a+cos²a)+cos²a
=sin²a×1+cos²a
=sin²a+cos²a
=1
得证;
(2)
tan²a-sin²a
=sin²a/cos²a-sin²a
=sin²a(1/cos²a-1)
=sin²a[(1-cos²a)/cos²a]
=sin²a[sin²a)/cos²a]
=sin²atan²a
=tan²asin²a
得证;