求此题答案及过程。
3个回答
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(1)
√(1+sin2)-√(1-sin2)
=√(sin²1+cos²1+2sin1cos1)-√(sin²1+cos²1-2sin1cos1)
=√(sin1+cos1)²-√(sin1-cos1)²
=(sin1+cos1)-(sin1-cos1)
=2cos1
(2)
√(1+cos2)-√(1-cos2)
=√(2cos²1)-√(2sin²1)
=√2cos1-√2sin1
(3)
(sin7°+cos15°sin8°)/(cos7°-sin15°sin8°)
=[sin(15°-8°)+cos15°sin8°]/[cos(15°-8°)-sin15°sin8°]
=(sin15°cos8°-cos15°sin8°+cos15°sin8°)/(cos15°cos8°+sin15°sin8°-sin15°sin8°)
=(sin15°cos8°)/(cos15°cos8°)
=tan15°
=2-√3
√(1+sin2)-√(1-sin2)
=√(sin²1+cos²1+2sin1cos1)-√(sin²1+cos²1-2sin1cos1)
=√(sin1+cos1)²-√(sin1-cos1)²
=(sin1+cos1)-(sin1-cos1)
=2cos1
(2)
√(1+cos2)-√(1-cos2)
=√(2cos²1)-√(2sin²1)
=√2cos1-√2sin1
(3)
(sin7°+cos15°sin8°)/(cos7°-sin15°sin8°)
=[sin(15°-8°)+cos15°sin8°]/[cos(15°-8°)-sin15°sin8°]
=(sin15°cos8°-cos15°sin8°+cos15°sin8°)/(cos15°cos8°+sin15°sin8°-sin15°sin8°)
=(sin15°cos8°)/(cos15°cos8°)
=tan15°
=2-√3
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