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Find all angles, 
0^(@) <= theta < 360^(@), that satisfy the equation below, to the nearest tenth of a degree.

4cos^(2)theta+17 cos theta+7=5cos theta+2
Answer: 
theta=

Find all angles, 0^{\circ} \leq \theta<360^{\circ} , that satisfy the equation below, to the nearest tenth of a degree.\newline4cos2θ+17cosθ+7=5cosθ+2 4 \cos ^{2} \theta+17 \cos \theta+7=5 \cos \theta+2 \newlineAnswer: θ= \theta=

Full solution

Q. Find all angles, 0θ<360 0^{\circ} \leq \theta<360^{\circ} , that satisfy the equation below, to the nearest tenth of a degree.\newline4cos2θ+17cosθ+7=5cosθ+2 4 \cos ^{2} \theta+17 \cos \theta+7=5 \cos \theta+2 \newlineAnswer: θ= \theta=
  1. Simplify Equation: Simplify the given equation by moving all terms to one side to set the equation to zero.\newline4cos2(θ)+17cos(θ)+7=5cos(θ)+24\cos^2(\theta) + 17\cos(\theta) + 7 = 5\cos(\theta) + 2\newline4cos2(θ)+17cos(θ)+75cos(θ)2=04\cos^2(\theta) + 17\cos(\theta) + 7 - 5\cos(\theta) - 2 = 0\newline4cos2(θ)+12cos(θ)+5=04\cos^2(\theta) + 12\cos(\theta) + 5 = 0
  2. Factor Quadratic: Factor the quadratic equation in terms of cos(θ)\cos(\theta). We are looking for factors of 4cos2(θ)4\cos^2(\theta) and 55 that add up to 12cos(θ)12\cos(\theta). (4cos(θ)+5)(cos(θ)+1)=0(4\cos(\theta) + 5)(\cos(\theta) + 1) = 0
  3. Solve First Factor: Solve each factor for cos(θ)\cos(\theta).\newlineFirst factor: 4cos(θ)+5=04\cos(\theta) + 5 = 0\newlinecos(θ)=54\cos(\theta) = -\frac{5}{4}\newlineSince the cosine of an angle cannot be less than 1-1 or greater than 11, this solution is not possible.
  4. Solve Second Factor: Solve the second factor for cos(θ)\cos(\theta).\newlineSecond factor: cos(θ)+1=0\cos(\theta) + 1 = 0\newlinecos(θ)=1\cos(\theta) = -1
  5. Find Angle: Find the angles θ\theta that correspond to cos(θ)=1\cos(\theta) = -1. The cosine of an angle is equal to 1-1 at θ=180\theta = 180 degrees.
  6. Check Range: Check the range for θ\theta.\newlineSince we are looking for angles between 00 degrees and 360360 degrees, the only angle that satisfies the equation and is within the range is θ=180\theta = 180 degrees.

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