Q. Find all angles, 0∘≤θ<360∘, that satisfy the equation below, to the nearest tenth of a degree.−7sin2θ−4sinθ+2=−1Answer: θ=
Simplify Equation: Simplify the given equation by adding 1 to both sides to set the equation to zero.−7sin2θ−4sinθ+2=−1−7sin2θ−4sinθ+2+1=0−7sin2θ−4sinθ+3=0
Factor Quadratic Equation: Factor the quadratic equation in terms of sin(θ). We are looking for two numbers that multiply to −7×3=−21 and add up to −4. These numbers are −7 and +3. So, we can write the equation as: (−7sin(θ)+3)(sin(θ)−1)=0
Solve for sin(θ): Solve each factor set to zero for sin(θ).First factor: −7sin(θ)+3=0−7sin(θ)=−3sin(θ)=73Second factor: sin(θ)−1=0sin(θ)=1
Find Corresponding Angles: Find the angles that correspond to sin(θ)=73 and sin(θ)=1 within the range 0^\circ \leq \theta < 360^\circ. For sin(θ)=1, the angle is 90∘ because sin(90∘)=1. For sin(θ)=73, we need to use the inverse sine function or a calculator to find the angles. Using a calculator, we find: θ=arcsin(73)≈25.4∘ Since the sine function is positive in the first and second quadrants, we also need to find the angle in the second quadrant. θ=180∘−25.4∘≈154.6∘
Verify Solutions: Verify that the angles found are within the given range and list all the solutions.The angles 90∘, 25.4∘, and 154.6∘ are all within the range 0^\circ \leq \theta < 360^\circ.Therefore, the solutions are θ≈25.4∘, 90∘, and 154.6∘.
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