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Solve the equations ( \( 95= \) gene 1) \( 3 \sin x-2 \cos x=0 \) 2) \( 3 \sin ^{2} x-2 \sin x=0 \) and 3) \( 3 \tan ^{2} x+\tan x=2 \) and -1 4) \( 5 \sin ^{2} x-3 \sin x-2=0 \)

Ask by Wood Ross. in South Africa
Mar 12,2025

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Answer

1. \( x = \arctan\left(\frac{2}{3}\right) + \pi k \), where \( k \) is an integer. 2. \( x = \pi k \) or \( x = \arcsin\left(\frac{2}{3}\right) + 2\pi k \) or \( x = \pi - \arcsin\left(\frac{2}{3}\right) + 2\pi k \), where \( k \) is an integer. 3. \( x = \arctan\left(\frac{2}{3}\right) + \pi k \) or \( x = -\frac{\pi}{4} + \pi k \), where \( k \) is an integer. 4. \( x = \frac{\pi}{2} + 2\pi k \) or \( x = -\arcsin(0.4) + 2\pi k \) or \( x = \pi + \arcsin(0.4) + 2\pi k \), where \( k \) is an integer.

Solution

1) We start with \[ 3\sin x - 2\cos x = 0. \] Rearrange the equation: \[ 3\sin x = 2\cos x. \] Assuming \(\cos x \neq 0\), divide both sides by \(\cos x\): \[ 3\tan x = 2 \quad\Longrightarrow\quad \tan x = \frac{2}{3}. \] Thus the general solution is \[ x = \arctan\left(\frac{2}{3}\right) + \pi k,\quad k\in\mathbb{Z}. \] 2) The equation is \[ 3\sin^2 x - 2\sin x = 0. \] Factor out \(\sin x\): \[ \sin x\,(3\sin x - 2) = 0. \] This gives two cases: • Case 1: \[ \sin x = 0 \quad\Longrightarrow\quad x = \pi k,\quad k\in\mathbb{Z}. \] • Case 2: \[ 3\sin x - 2 = 0\quad\Longrightarrow\quad \sin x = \frac{2}{3}. \] The general solution for \(\sin x = \frac{2}{3}\) is \[ x = \arcsin\left(\frac{2}{3}\right) + 2\pi k \quad \text{or} \quad x = \pi - \arcsin\left(\frac{2}{3}\right) + 2\pi k,\quad k\in\mathbb{Z}. \] 3) The equation is \[ 3\tan^2 x + \tan x - 2 = 0. \] Let \(y = \tan x\). Then the quadratic becomes \[ 3y^2 + y - 2 = 0. \] Compute the discriminant: \[ \Delta = 1^2 - 4(3)(-2) = 1 + 24 = 25. \] Solve for \(y\): \[ y = \frac{-1\pm \sqrt{25}}{6} = \frac{-1\pm 5}{6}. \] This gives the solutions: \[ y = \frac{4}{6} = \frac{2}{3} \quad \text{or} \quad y = \frac{-6}{6} = -1. \] Thus we have two cases: • Case 1: \[ \tan x = \frac{2}{3}\quad\Longrightarrow\quad x = \arctan\left(\frac{2}{3}\right) + \pi k,\quad k\in\mathbb{Z}. \] • Case 2: \[ \tan x = -1\quad\Longrightarrow\quad x = -\frac{\pi}{4} + \pi k,\quad k\in\mathbb{Z}. \] 4) The equation is \[ 5\sin^2 x - 3\sin x - 2=0. \] Let \(y = \sin x\). Then the quadratic is \[ 5y^2 - 3y - 2 = 0. \] Compute the discriminant: \[ \Delta = (-3)^2 - 4(5)(-2) = 9 + 40 = 49. \] Solve for \(y\): \[ y = \frac{3 \pm 7}{10}. \] This gives: \[ y = \frac{10}{10} = 1 \quad \text{or} \quad y = \frac{-4}{10} = -0.4. \] Now solve for \(x\): • Case 1: \(\sin x = 1\) gives \[ x = \frac{\pi}{2} + 2\pi k,\quad k\in\mathbb{Z}. \] • Case 2: \(\sin x = -0.4\) gives \[ x = \arcsin(-0.4) + 2\pi k \quad \text{or} \quad x = \pi - \arcsin(-0.4) + 2\pi k,\quad k\in\mathbb{Z}. \] Since \(\arcsin(-0.4) = -\arcsin(0.4)\), the solutions can also be written as \[ x = -\arcsin(0.4) + 2\pi k \quad \text{or} \quad x = \pi + \arcsin(0.4) + 2\pi k,\quad k\in\mathbb{Z}. \]

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Beyond the Answer

To tackle these equations, let's break each down step-by-step in a precise and engaging manner! 1) For the equation \( 3 \sin x - 2 \cos x = 0 \), we can rearrange it to find \( \frac{\sin x}{\cos x} = \frac{2}{3} \), leading to \( \tan x = \frac{2}{3} \). This gives the solutions \( x = \tan^{-1}\left(\frac{2}{3}\right) + k\pi \) where \( k \) is any integer. 2) In \( 3 \sin^{2} x - 2 \sin x = 0 \), we factor out a \( \sin x \) to get \( \sin x (3 \sin x - 2) = 0 \). This provides two cases: \( \sin x = 0 \) (which gives solutions like \( x = n\pi \) for integers \( n \)), and \( 3 \sin x - 2 = 0 \), resulting in \( \sin x = \frac{2}{3} \) with solutions \( x = \sin^{-1}\left(\frac{2}{3}\right) + 2k\pi \) and \( x = \pi - \sin^{-1}\left(\frac{2}{3}\right) + 2k\pi \). 3) Moving to \( 3 \tan^{2} x + \tan x - 2 = 0 \), we can treat this as a quadratic in terms of \( y = \tan x \), giving \( 3y^2 + y - 2 = 0 \). Using the quadratic formula, \( y = \frac{-1 \pm \sqrt{1 + 24}}{6} = \frac{-1 \pm 5}{6} \), thus \( y = \frac{2}{3} \) or \( y = -1 \). Hence, \( \tan x = \frac{2}{3} \) or \( \tan x = -1 \) leads to \( x = \tan^{-1}\left(\frac{2}{3}\right) + k\pi \) and \( x = \frac{3\pi}{4} + k\pi \). 4) Lastly, for \( 5 \sin^{2} x - 3 \sin x - 2 = 0 \), we use the quadratic formula with \( \sin x \) as the variable: \( a = 5, b = -3, c = -2 \). Calculating the discriminant \( (-3)^2 - 4 \cdot 5 \cdot (-2) = 9 + 40 = 49 \), we find \( \sin x = \frac{3 \pm 7}{10} \), leading to solutions \( \sin x = 1 \) or \( \sin x = -\frac{2}{5} \). Thus, \( x = \frac{\pi}{2} + 2k\pi \) or \( x = \sin^{-1}\left(-\frac{2}{5}\right) + 2k\pi \) and \( x = \pi - \sin^{-1}\left(-\frac{2}{5}\right) + 2k\pi \). With these equations solved, math enthusiasts can rejoice in the variety of solutions derived!

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