Proving Trig Identity: (Sin2x-tanx)/cos2x=tanx

In summary, a trigonometric identity is a mathematical equation that holds true for all values of the variables involved. To prove a trigonometric identity, one must manipulate one side of the equation using known identities and properties until it is equivalent to the other side. For the specific identity of (Sin2x-tanx)/cos2x=tanx, the process involves using the double angle and quotient identities for sine and tangent, respectively. It is important to note that some identities may only hold true for certain values of the variables, and proving trigonometric identities can be useful in various real-world applications such as physics, engineering, and navigation.
  • #1
paix1988
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May someone kindly assist me to prove this trig identity

(Sin2x-tanx) / cos2x = tanx

Thank you for your assistance
 
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  • #2
paix1988 said:
May someone kindly assist me to prove this trig identity

(Sin2x-tanx) / cos2x = tanx

Thank you for your assistance

Making use of the identities $\sin 2x = 2 \sin x \cos x$ and $\tan x = \sin x / \cos x$ we can write the RHS as:
$$\frac{2 \sin x \cos x -\frac{\sin x}{\cos x}}{\cos 2x}.$$
To proceed, write the numerator as one fraction (thus with denominator $\cos x$) and factorize!
 

FAQ: Proving Trig Identity: (Sin2x-tanx)/cos2x=tanx

What is the definition of a trigonometric identity?

A trigonometric identity is a mathematical equation that is true for all values of the variables involved. In other words, it is an identity that holds true regardless of the values of the angles involved.

How do you prove a trigonometric identity?

To prove a trigonometric identity, you must manipulate one side of the equation using known trigonometric identities and properties until it is equivalent to the other side. This can involve simplifying, expanding, or substituting in different trigonometric expressions.

What is the process for proving the identity (Sin2x-tanx)/cos2x=tanx?

The process for proving this identity involves using the double angle identity for sine (sin2x = 2sinx cosx) and the quotient identity for tangent (tanx = sinx/cosx). Substituting these identities into the equation and manipulating both sides will eventually lead to the equation being simplified to tanx, proving the identity.

Are there any special cases or restrictions when proving trigonometric identities?

Yes, it is important to note that some trigonometric identities may only hold true for certain values of the variables. For example, the identity (Sin2x-tanx)/cos2x=tanx may not hold true for values of x that make the denominator (cos2x) equal to 0, as division by 0 is undefined.

How can proving trigonometric identities be useful in real-world applications?

Proving trigonometric identities is useful in many fields, such as physics, engineering, and navigation. It allows for the simplification of complex trigonometric expressions, making calculations and problem-solving more efficient. It also helps in verifying the accuracy of mathematical models and equations used in real-world situations.

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