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 By expressing 
sqrt3sin x+3cos x in the form 
A sin(x+alpha), solve
4

sqrt3sin x+3cos x=sqrt3, for 
0 <= x <= 2pi.

By expressing \newline3sinx+3cosx\sqrt{3}\sin x+3\cos x in the form Asin(x+α)A \sin(x+\alpha), solve3sinx+3cosx=3\sqrt{3}\sin x+3\cos x=\sqrt{3}, for \newline0x2π0 \leq x \leq 2\pi.

Full solution

Q. By expressing \newline3sinx+3cosx\sqrt{3}\sin x+3\cos x in the form Asin(x+α)A \sin(x+\alpha), solve3sinx+3cosx=3\sqrt{3}\sin x+3\cos x=\sqrt{3}, for \newline0x2π0 \leq x \leq 2\pi.
  1. Use Trigonometric Identity: We want to express 3sin(x)+3cos(x)\sqrt{3}\sin(x) + 3\cos(x) in the form Asin(x+α)A \sin(x+\alpha). To do this, we will use the identity sin(x+α)=sin(x)cos(α)+cos(x)sin(α)\sin(x+\alpha) = \sin(x)\cos(\alpha) + \cos(x)\sin(\alpha).
  2. Match Coefficients: Let Asin(x+α)=A(sin(x)cos(α)+cos(x)sin(α))A \sin(x+\alpha) = A(\sin(x)\cos(\alpha) + \cos(x)\sin(\alpha)). We want to match the coefficients of sin(x)\sin(x) and cos(x)\cos(x) to those in 3sin(x)+3cos(x)\sqrt{3}\sin(x) + 3\cos(x).
  3. Solve Equations for AA: Matching coefficients, we get Acos(α)=3A \cos(\alpha) = \sqrt{3} and Asin(α)=3A \sin(\alpha) = 3. We can solve these two equations to find AA and α\alpha.
  4. Find A Using Pythagorean Identity: To find A, we use the Pythagorean identity: A2=(Acos(α))2+(Asin(α))2A^2 = (A \cos(\alpha))^2 + (A \sin(\alpha))^2. Substituting the values we have A2=(3)2+32=3+9=12A^2 = (\sqrt{3})^2 + 3^2 = 3 + 9 = 12.
  5. Find AA and A\Alpha: Taking the square root of both sides, we get A=12=23A = \sqrt{12} = 2\sqrt{3}.
  6. Express in Desired Form: To find α\alpha, we take the ratio of the two equations: tan(α)=Asin(α)Acos(α)=33=3\tan(\alpha) = \frac{A \sin(\alpha)}{A \cos(\alpha)} = \frac{3}{\sqrt{3}} = \sqrt{3}.
  7. Isolate sin(x+α)\sin(x + \alpha): Using the arctan\arctan function, we find α=arctan(3)\alpha = \arctan(\sqrt{3}). Since we are looking for solutions in the interval [0,2π][0, 2\pi], we consider the principal value of arctan(3)\arctan(\sqrt{3}), which is π/3\pi/3.
  8. Find Solutions for sin(y)\sin(y): Now we have expressed 3sin(x)+3cos(x)\sqrt{3}\sin(x) + 3\cos(x) as 23sin(x+π/3)2 \sqrt{3} \sin(x + \pi/3). We can now solve the equation 23sin(x+π/3)=32 \sqrt{3} \sin(x + \pi/3) = \sqrt{3}.
  9. Substitute x+αx + \alpha for yy: Divide both sides by 232 \sqrt{3} to isolate sin(x+π/3)\sin(x + \pi/3): sin(x+π/3)=323=12\sin(x + \pi/3) = \frac{\sqrt{3}}{2 \sqrt{3}} = \frac{1}{2}.
  10. Solve for x: We look for solutions to sin(x+π3)=12\sin(x + \frac{\pi}{3}) = \frac{1}{2}. The solutions to sin(y)=12\sin(y) = \frac{1}{2} are y=π6+2kπy = \frac{\pi}{6} + 2k\pi and y=5π6+2kπy = \frac{5\pi}{6} + 2k\pi, where kk is an integer.
  11. Check Solutions in Interval: Substitute x+π3x + \frac{\pi}{3} for yy: x+π3=π6+2kπx + \frac{\pi}{3} = \frac{\pi}{6} + 2k\pi or x+π3=5π6+2kπx + \frac{\pi}{3} = \frac{5\pi}{6} + 2k\pi. We solve for xx in each case.
  12. Final Solutions: For the first equation: x=π6π3+2kπ=π6+2kπx = \frac{\pi}{6} - \frac{\pi}{3} + 2k\pi = -\frac{\pi}{6} + 2k\pi. For the second equation: x=5π6π3+2kπ=π2+2kπx = \frac{5\pi}{6} - \frac{\pi}{3} + 2k\pi = \frac{\pi}{2} + 2k\pi.
  13. Final Solutions: For the first equation: x=π6π3+2kπ=π6+2kπx = \frac{\pi}{6} - \frac{\pi}{3} + 2k\pi = -\frac{\pi}{6} + 2k\pi. For the second equation: x=5π6π3+2kπ=π2+2kπx = \frac{5\pi}{6} - \frac{\pi}{3} + 2k\pi = \frac{\pi}{2} + 2k\pi.We need to find the values of xx in the interval [0,2π][0, 2\pi]. For the first equation, x=π6x = -\frac{\pi}{6} is not in the interval, but x=π6+2π=11π6x = -\frac{\pi}{6} + 2\pi = \frac{11\pi}{6} is. For the second equation, x=π2x = \frac{\pi}{2} is in the interval.
  14. Final Solutions: For the first equation: x=π6π3+2kπ=π6+2kπx = \frac{\pi}{6} - \frac{\pi}{3} + 2k\pi = -\frac{\pi}{6} + 2k\pi. For the second equation: x=5π6π3+2kπ=π2+2kπx = \frac{5\pi}{6} - \frac{\pi}{3} + 2k\pi = \frac{\pi}{2} + 2k\pi.We need to find the values of xx in the interval [0,2π][0, 2\pi]. For the first equation, x=π6x = -\frac{\pi}{6} is not in the interval, but x=π6+2π=11π6x = -\frac{\pi}{6} + 2\pi = \frac{11\pi}{6} is. For the second equation, x=π2x = \frac{\pi}{2} is in the interval.The solutions to the equation 3sin(x)+3cos(x)=3\sqrt{3}\sin(x) + 3\cos(x) = \sqrt{3} in the interval [0,2π][0, 2\pi] are x=11π6x = \frac{11\pi}{6} and x=π2x = \frac{\pi}{2}.

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