Q. Find all angles, 0∘≤θ<360∘, that satisfy the equation below, to the nearest tenth of a degree.8sin2θ+6sinθ=−1Answer: θ=
Rewrite Equation in Quadratic Form: Rewrite the given equation in a quadratic form by substituting sin(θ) with a variable, let's say 'x'. This gives us the equation 8x2+6x+1=0.
Calculate Discriminant: Calculate the discriminant, which is b2−4ac=62−4(8)(1)=36−32=4.
Find Solutions for x: Since the discriminant is positive, there are two real solutions for x. Calculate these solutions using the quadratic formula:x=2⋅8−6±4x=16−6±2
Find Angles for sin(θ)=−41: Find the two values of x:x1=16(−6+2)=16−4=−41x2=16(−6−2)=16−8=−21
Find Angles for sin(θ)=−21: Recall that x represents sin(θ). Since the range of the sine function is [−1,1], both solutions x1=−41 and x2=−21 are valid for sine values. We need to find the corresponding anglesθ for these sine values.
Find Angles for sin(θ)=−21: Recall that x represents sin(θ). Since the range of the sine function is [−1,1], both solutions x1=−41 and x2=−21 are valid for sine values. We need to find the corresponding angles θ for these sine values.Find the angles corresponding to sin(θ)=−41. Since the sine function is negative in the third and fourth quadrants, we look for angles in those quadrants. Use the inverse sine function to find the reference angle, and then find the actual angles.θ1=arcsin(−41)≈−14.5 degrees (reference angle)The actual angles are:θ1=180+14.5≈194.5 degrees (third quadrant)x0 degrees (fourth quadrant)
Find Angles for sin(θ)=−21: Recall that x represents sin(θ). Since the range of the sine function is [−1,1], both solutions x1=−41 and x2=−21 are valid for sine values. We need to find the corresponding angles θ for these sine values.Find the angles corresponding to sin(θ)=−41. Since the sine function is negative in the third and fourth quadrants, we look for angles in those quadrants. Use the inverse sine function to find the reference angle, and then find the actual angles.θ1=arcsin(−41)≈−14.5 degrees (reference angle)The actual angles are:θ1=180+14.5≈194.5 degrees (third quadrant)x0 degrees (fourth quadrant)Find the angles corresponding to sin(θ)=−21. Again, since the sine function is negative in the third and fourth quadrants, we look for angles in those quadrants. Use the inverse sine function to find the reference angle, and then find the actual angles.x2 degrees (reference angle)The actual angles are:x3 degrees (third quadrant)x4 degrees (fourth quadrant)
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