Prove 2( cos y + sin y) =(sec y)(1+cos 2y + sin2y)

[Cherting]

Prove 2( cos y + sin y) =(sec y)(1+cos 2y + sin2y)

 

[Deleted member 4993]

Prove 2( cos y + sin y) =(sec y)(1+cos 2y + sin2y)

Hint: use cos(2y) = 2*cos²(y) - 1

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[stapel]

Prove 2( cos y + sin y) =(sec y)(1+cos 2y + sin2y)

Just to be clear, are you using the notation "sin2y" to mean "sin²(y)" or "sin(2y)"? (Same question for the cosine.)

When you reply, please show all of your efforts so far, starting with your conversion of everything to sines and cosines, and multiplying everything out. Thank you!