Is Cos2x the Same as Cos^2(x) in the Equation Cos2x + Cosx + 1 = 0?

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In the equation cos2x + cosx + 1 = 0, cos2x is not the same as cos^2x; it represents the cosine of double the angle. To solve the equation, one should use the double angle identity for cosine, which can simplify the expression. The discussion emphasizes the importance of understanding trigonometric identities, particularly how to express 1 in terms of sine and cosine. Ultimately, this leads to a quadratic equation in terms of cosx, which can be solved using standard methods. Understanding these concepts is crucial for solving trigonometric equations effectively.
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Solve please give me some help

how would you solve this question cos2x+cosx+1=0? The cos2x is throwing me off is that the same as cos^2x? Its multiple choice and all the answers are in radian how come?
 
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1. cos(a + b) = cos(a)cos(b) - sin(a)sin(b).
2. Do you know how to write 1 in terms of sin and cos?
 
AKG said:
1. cos(a + b) = cos(a)cos(b) - sin(a)sin(b).
2. Do you know how to write 1 in terms of sin and cos?

no i don't please help me
 
\sin^{2}x + \cos^{2}x = 1
 
cos2x is not the same as cos^2x. Use a double angle identity for that one.
 
On normal basis,u should end up with a simple quadratic equation is "\cos x"...That won't be 2 hard to solve...

Daniel.
 
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