(adsbygoogle = window.adsbygoogle || []).push({}); Please help me in these identities!!!!

I tried to solve these identities, but I don't think that these are identities exept the first,

1.) sin2α/1+cos2α=tanα

2.) 1-cosα/sinα=tanα/2

3.) tanα+ctanα=csecα

4.) 3cosα+cos3α/3sinα-sin3α=3/2

5.) sin18°+sin30°=sin54

At first i did this:

sin2α=2sinα*cosα

cos2α=cos^2α-sin^2α

1=cos^2α+sin^2α

sin2α/1+cos2α=2sinα*cosα/cos^2α+sin^2α+cos^2α-sin^2α=...=tanα

But I don't know what to do eith others i tried to substitute tanα=sinα/cosα and etc but no solve ,

please help me

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# Homework Help: Please help me in these identities

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