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AngelofnoColour
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#1
Report Thread starter 15 years ago
#1
Ive done this question about 10 times, and still cant prove it. Ive looked at the answers and just dont understand them.
Please can someone prove this, in nice easy steps, please


Prove that:
2tanx - sin2x = 2sin^2x.tanx
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lgs98jonee
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#2
Report 15 years ago
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(Original post by BlueAngel)
Ive done this question about 10 times, and still cant prove it. Ive looked at the answers and just dont understand them.
Please can someone prove this, in nice easy steps, please


Prove that:
2tanx - sin2x = 2sin^2x.tanx
2tanx-sin2x=2tanx-2sinxcosx
=2sinx/cosx-2sinxcosx
=(2sinx-2sinxcos^2x)/cosx [times top and bottom by cosx]
=tanx(2-2cos^2x) [sinx/cosx=tanx ]
=tanx(2-2(1-sin^2x) [sin^2x=1-cos^2x]
=tanx(2+2sin^2x-2)
=tanx(2sin^2x)
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JamesF
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#3
Report 15 years ago
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On the right, make sin^2 = 1-cos^2, so you get
2sin^2xtanx = (2 - 2cos^2x)tanx = 2tanx - 2cosxsinx = 2tanx - sin2x
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AngelofnoColour
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#4
Report Thread starter 15 years ago
#4
thank you all.
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