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(3) \( \frac{\cos ^{2} x}{1+\sin x}=1-\tan x \cos x \)

Ask by Dawson Turner. in South Africa
Mar 09,2025

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Answer

The solution to the equation \( \frac{\cos ^{2}x}{1+\sin x}=1-\tan x\cos x \) is all real numbers except \( x = \frac{\pi}{2} + k\pi \) where \( k \) is any integer.

Solution

Solve the equation \( \frac{\cos ^{2}x}{1+\sin x}=1-\tan x\cos x \). Solve the equation by following steps: - step0: Solve for \(x\): \(\frac{\cos^{2}\left(x\right)}{1+\sin\left(x\right)}=1-\tan\left(x\right)\cos\left(x\right)\) - step1: Find the domain: \(\frac{\cos^{2}\left(x\right)}{1+\sin\left(x\right)}=1-\tan\left(x\right)\cos\left(x\right),x\neq \frac{\pi }{2}+k\pi ,k \in \mathbb{Z}\) - step2: Rewrite the expression: \(\frac{\cos^{2}\left(x\right)}{1+\sin\left(x\right)}=1-\frac{\sin\left(x\right)}{\cos\left(x\right)}\times \cos\left(x\right)\) - step3: Rewrite the expression: \(\frac{\cos^{2}\left(x\right)}{1+\sin\left(x\right)}=1-\frac{\sin\left(x\right)\cos\left(x\right)}{\cos\left(x\right)}\) - step4: Multiply both sides of the equation by LCD: \(\frac{\cos^{2}\left(x\right)}{1+\sin\left(x\right)}\times \left(1+\sin\left(x\right)\right)\cos\left(x\right)=\left(1-\frac{\sin\left(x\right)\cos\left(x\right)}{\cos\left(x\right)}\right)\left(1+\sin\left(x\right)\right)\cos\left(x\right)\) - step5: Simplify the equation: \(\cos^{3}\left(x\right)=\left(1+\sin\left(x\right)\right)\cos\left(x\right)-\sin\left(x\right)\cos\left(x\right)\left(1+\sin\left(x\right)\right)\) - step6: Move the expression to the left side: \(\cos^{3}\left(x\right)-\left(\left(1+\sin\left(x\right)\right)\cos\left(x\right)-\sin\left(x\right)\cos\left(x\right)\left(1+\sin\left(x\right)\right)\right)=0\) - step7: Calculate: \(\cos^{3}\left(x\right)+\left(-1-\sin\left(x\right)\right)\cos\left(x\right)+\sin\left(x\right)\cos\left(x\right)\left(1+\sin\left(x\right)\right)=0\) - step8: Factor the expression: \(\cos\left(x\right)\left(\cos^{2}\left(x\right)-1+\sin^{2}\left(x\right)\right)=0\) - step9: Separate into possible cases: \(\begin{align}&\cos\left(x\right)=0\\&\cos^{2}\left(x\right)-1+\sin^{2}\left(x\right)=0\end{align}\) - step10: Solve the equation: \(\begin{align}&x=\frac{\pi }{2}+k\pi ,k \in \mathbb{Z}\\&x \in \mathbb{R}\end{align}\) - step11: Find the union: \(x \in \mathbb{R}\) - step12: Check if the solution is in the defined range: \(x \in \mathbb{R},x\neq \frac{\pi }{2}+k\pi ,k \in \mathbb{Z}\) - step13: Find the intersection: \(x\neq \frac{\pi }{2}+k\pi ,k \in \mathbb{Z}\) The solution to the equation \( \frac{\cos ^{2}x}{1+\sin x}=1-\tan x\cos x \) is \( x \neq \frac{\pi}{2}+k\pi \) where \( k \in \mathbb{Z} \).

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Beyond the Answer

To solve the equation \( \frac{\cos ^{2} x}{1+\sin x}=1-\tan x \cos x \), we can start by simplifying both sides. First, recall that \(\tan x = \frac{\sin x}{\cos x}\). Therefore, we can rewrite the right-hand side: \[ 1 - \tan x \cos x = 1 - \sin x \] Now, we need to simplify the left side. The left-hand side can be rewritten as: \[ \frac{\cos^2 x}{1+\sin x} \] Now, let's see if we can set both sides equal to each other. We will find a common denominator for the left-hand side to better analyze the equality: Multiply the left-side numerator and denominator by \(1 - \sin x\): \[ \frac{\cos^2 x (1 - \sin x)}{(1 + \sin x)(1 - \sin x)} \] The denominator simplifies via the difference of squares: \[ 1 - \sin^2 x = \cos^2 x \] Putting it all together, we have: \[ \frac{\cos^2 x (1 - \sin x)}{\cos^2 x} = 1 - \sin x \] This is equal to our right-hand side, verifying that the equation holds: \[ 1 - \sin x = 1 - \sin x \] Thus, the original equation is confirmed as true for values where \( \cos x \neq 0 \) and \( 1 + \sin x \neq 0 \).

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