Q. Solve the equation.2sin2θ−3−sin2θ−16=0 for 0≤θ≤π,θ=4π
Simplify Equation: Let's first simplify the given equation 2sin(2θ)−3−sin(2θ)−16=0 by finding a common denominator and combining the terms.
Find Common Denominator: The common denominator for the terms 2sin(2θ)−3 and −sin(2θ)−16 is sin(2θ)−1. We multiply the term 2sin(2θ)−3 by sin(2θ)−1sin(2θ)−1 to get a common denominator.
Expand Equation: After finding the common denominator, the equation becomes: egin{equation}(2\sin(2\theta) - 3)(\sin(2\theta) - 1) - 6 = 0egin{equation}
Quadratic Equation in u: Expanding the left side of the equation, we get: 2sin2(2θ)−2sin(2θ)−3sin(2θ)+3−6=0
Solve Quadratic Equation: Combining like terms, the equation simplifies to: 2sin2(2θ)−5sin(2θ)−3=0
Possible Solutions for u: This is a quadratic equation in terms of sin(2θ). Let's set u=sin(2θ) and rewrite the equation as:2u2−5u−3=0
Select Valid Solution: Now we need to solve the quadratic equation 2u2−5u−3=0. We can use the quadratic formulau=2a−b±b2−4ac where a=2, b=−5, and c=−3.
Find theta: Plugging the values into the quadratic formula, we get:u=2⋅25±(−5)2−4⋅2⋅(−3)u=45±25+24u=45±49u=45±7
Consider Principal Values: This gives us two possible solutions for u:u=45+7=412=3u=45−7=4−2=−0.5
Find Corresponding Values: Since u=sin(2θ), we have sin(2θ)=3 and sin(2θ)=−0.5. However, the sine function has a range of [−1,1], so sin(2θ)=3 is not possible.
Divide by 2: We only consider the solution sin(2θ)=−0.5. To find θ, we need to solve 2θ=arcsin(−0.5).
Final Valid Solutions: The arcsine of −0.5 is −6π or 611π when considering the principal values. However, since we are looking for θ in the range [0,π], we need to find the corresponding values for 2θ in this range.
Final Valid Solutions: The arcsine of −0.5 is −π/6 or 11π/6 when considering the principal values. However, since we are looking for θ in the range [0,π], we need to find the corresponding values for 2θ in this range.The values of 2θ that correspond to sin(2θ)=−0.5 in the range [0,2π] are 7π/6 and 11π/6. We divide these by −π/61 to find the values of θ.
Final Valid Solutions: The arcsine of −0.5 is −π/6 or 11π/6 when considering the principal values. However, since we are looking for θ in the range [0,π], we need to find the corresponding values for 2θ in this range.The values of 2θ that correspond to sin(2θ)=−0.5 in the range [0,2π] are 7π/6 and 11π/6. We divide these by −π/61 to find the values of θ.Dividing by −π/61, we get −π/64 and −π/65. Both of these values are within the range [0,π].
Final Valid Solutions: The arcsine of −0.5 is −π/6 or 11π/6 when considering the principal values. However, since we are looking for θ in the range [0,π], we need to find the corresponding values for 2θ in this range.The values of 2θ that correspond to sin(2θ)=−0.5 in the range [0,2π] are 7π/6 and 11π/6. We divide these by −π/61 to find the values of θ.Dividing by −π/61, we get −π/64 and −π/65. Both of these values are within the range [0,π].We must also remember the restriction −π/67. Since neither −π/68 nor −π/69 is equal to 11π/60, both solutions are valid.