Trigonometric Identities and EquationsUsing a Pythagorean identity to find solutions in an interval for a trigonometri...Find all solutions of the equation in the interval [0,2π).4cosx=−sin2x+4Write your answer in radians in terms of π.If there is more than one solution, separate them with commas.
Q. Trigonometric Identities and EquationsUsing a Pythagorean identity to find solutions in an interval for a trigonometri...Find all solutions of the equation in the interval [0,2π).4cosx=−sin2x+4Write your answer in radians in terms of π.If there is more than one solution, separate them with commas.
Rewrite using Pythagorean identity: Rewrite the equation using a Pythagorean identity.We know that sin2(x)+cos2(x)=1, so we can rewrite sin2(x) as 1−cos2(x).The equation becomes 4cos(x)=−(1−cos2(x))+4.
Simplify the equation: Simplify the equation.Distribute the negative sign on the right side of the equation to get 4cos(x)=−1+cos2(x)+4.Combine like terms to get 4cos(x)=cos2(x)+3.
Rearrange for quadratic equation: Rearrange the equation to form a quadratic equation in terms of cos(x). Subtract 4cos(x) from both sides to get 0=cos2(x)−4cos(x)+3.
Factor the quadratic equation: Factor the quadratic equation.We are looking for factors of 3 that add up to −4. The factors are −1 and −3.So, the factored form is 0=(cos(x)−1)(cos(x)−3).
Solve for cos(x): Solve for cos(x).Set each factor equal to zero: cos(x)−1=0 and cos(x)−3=0.Solving for cos(x) gives us cos(x)=1 and cos(x)=3.However, the cosine of an angle cannot be greater than 1, so cos(x)=3 has no solution.
Find angles for cos(x): Find the angles for cos(x)=1. The only angle in the interval [0,2π) where cos(x)=1 is x=0.
More problems from Inverses of sin, cos, and tan: radians