已知sina=根号5/5,则sin^4a-cos^4a的值为_____,
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已知sina=根号5/5,则sin^4a-cos^4a的值为_____,
已知sina=根号5/5,则sin^4a-cos^4a的值为_____,
已知sina=根号5/5,则sin^4a-cos^4a的值为_____,
sina=√5/5
∴cosa=±√1-sin²a=±2√5/5
sin^4a-cos^4a
=(sin²a+cos²a)(sin²a-cos²a)
=sin²a-cos²a
=(√5/5)²-(±2√5/5)²
=1/5-4/5
=-3/5
sin^4a-cos^4a
=sin^2a-cos^2a=2sin²a-1
=2*(1/5)-1
=-3/5
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