Find all angles, 0^{\circ} \leq \theta<360^{\circ} , that satisfy the equation below, to the nearest tenth of a degree.8sin2θ−11sinθ−6=−9sinθ−3Answer: θ=
Q. Find all angles, 0∘≤θ<360∘, that satisfy the equation below, to the nearest tenth of a degree.8sin2θ−11sinθ−6=−9sinθ−3Answer: θ=
Simplify the equation: First, we need to simplify the given equation by moving all terms to one side to set the equation to zero.8sin2θ−11sinθ−6=−9sinθ−3Adding 9sinθ and 3 to both sides, we get:8sin2θ−11sinθ+9sinθ−6+3=08sin2θ−2sinθ−3=0
Factor the quadratic equation: Next, we factor the quadratic equation in terms of sinθ. We look for two numbers that multiply to (8)(−3)=−24 and add up to −2. The numbers −6 and +4 satisfy these conditions. So we can write the equation as: (8sin2θ+4sinθ)−(6sinθ+3)=0
Factor by grouping: Now, we factor by grouping.First group: 8sin2θ+4sinθ=4sinθ(2sinθ+1)Second group: −6sinθ−3=−3(2sinθ+1)The equation becomes:4sinθ(2sinθ+1)−3(2sinθ+1)=0
Factor out common factor: We can now factor out the common factor (2sinθ+1):(2sinθ+1)(4sinθ−3)=0
Set factors equal to zero: We set each factor equal to zero and solve for sinθ:2sinθ+1=0 or 4sinθ−3=0 For the first equation: 2sinθ=−1 => sinθ=−21 For the second equation: 4sinθ=3 => sinθ=43
Find angles for sinθ=−21: We find the angles for sinθ=−21. Since the sine function is negative in the third and fourth quadrants, we look for angles in those quadrants. The reference angle whose sine is 21 is 30 degrees. Therefore, the angles are 180+30=210 degrees and 360−30=330 degrees.
Find angles for sinθ=43: We find the angles for sinθ=43. This is not a standard value for the sine function, so we will use a calculator to find the angle. Using the inverse sine function, we find: θ=sin−1(43)θ≈48.6 degrees (to the nearest tenth) Since the sine function is positive in the first and second quadrants, the other angle is 180−48.6=131.4 degrees.
Final angles: We now have all the angles that satisfy the equation: θ≈48.6 degrees, 131.4 degrees, 210 degrees, and 330 degrees.
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