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# Couple of basic C3 questions I'm really stuck on. Any help is greatly appreciated. Watch

1. So guys, I've got a few basic C3 questions and I'm really stuck on them, would anyone possibly be able to provide some help?

Questions are:

• Find those values of t, to 2 d.p. for which 4sec3 - 7sect + 3 = 0, 0 < t < 2pi
• Solve the equation (secx-cosx)2 = tanx - sin2x on the interval -2pi < x < 2pi
• Prove that cos(x+pi/6) + sin(x+pi/3) = (squareroot of 3)cosx

Any help would be really appreciated. Thanks a lot.
2. (Original post by decb24)
So guys, I've got a few basic C3 questions and I'm really stuck on them, would anyone possibly be able to provide some help?

Questions are:
Find those values of t, to 2 d.p. for which 4sec3 - 7sect + 3 = 0, 0 < t < 2pi
I assume that this is

It should be clear that one possible solution is that

Treat this like any other cubic - divide by and find the solutions for the corresponding quadratic
3. (Original post by decb24)
So guys, I've got a few basic C3 questions and I'm really stuck on them, would anyone possibly be able to provide some help?

Questions are:

• Find those values of t, to 2 d.p. for which 4sec3 - 7sect + 3 = 0, 0 < t < 2pi
• Solve the equation (secx-cosx)2 = tanx - sin2x on the interval -2pi < x < 2pi
• Prove that cos(x+pi/6) + sin(x+pi/3) = (squareroot of 3)cosx

Any help would be really appreciated. Thanks a lot.
For the third one just use the addition theorems to expand the two terms on the left and use the known values for sin and cos

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