The problem consists of several calculus questions, including finding roots of equations, ranges and domains of functions, verifying trigonometric identities, solving trigonometric equations, determining if functions are odd or even, and finding derivatives. I will solve question 3a(i). The question asks to find all solutions to the problem $\sin(2\theta) = \tan(\theta)$.

TrigonometryTrigonometric EquationsDouble Angle IdentityTrigonometric IdentitiesSolving Equations
2025/3/14

1. Problem Description

The problem consists of several calculus questions, including finding roots of equations, ranges and domains of functions, verifying trigonometric identities, solving trigonometric equations, determining if functions are odd or even, and finding derivatives. I will solve question 3a(i). The question asks to find all solutions to the problem sin(2θ)=tan(θ)\sin(2\theta) = \tan(\theta).

2. Solution Steps

We are asked to find all solutions to the equation sin(2θ)=tan(θ)\sin(2\theta) = \tan(\theta).
We can use the double-angle identity for sine:
sin(2θ)=2sin(θ)cos(θ)\sin(2\theta) = 2\sin(\theta)\cos(\theta).
Then, our equation becomes 2sin(θ)cos(θ)=tan(θ)2\sin(\theta)\cos(\theta) = \tan(\theta).
Since tan(θ)=sin(θ)cos(θ)\tan(\theta) = \frac{\sin(\theta)}{\cos(\theta)}, we can rewrite the equation as 2sin(θ)cos(θ)=sin(θ)cos(θ)2\sin(\theta)\cos(\theta) = \frac{\sin(\theta)}{\cos(\theta)}.
Rearranging, we get 2sin(θ)cos(θ)sin(θ)cos(θ)=02\sin(\theta)\cos(\theta) - \frac{\sin(\theta)}{\cos(\theta)} = 0.
Factoring out sin(θ)\sin(\theta), we have sin(θ)(2cos(θ)1cos(θ))=0\sin(\theta)\left(2\cos(\theta) - \frac{1}{\cos(\theta)}\right) = 0.
This implies that either sin(θ)=0\sin(\theta) = 0 or 2cos(θ)1cos(θ)=02\cos(\theta) - \frac{1}{\cos(\theta)} = 0.
If sin(θ)=0\sin(\theta) = 0, then θ=nπ\theta = n\pi, where nn is an integer.
If 2cos(θ)1cos(θ)=02\cos(\theta) - \frac{1}{\cos(\theta)} = 0, then 2cos2(θ)1=02\cos^2(\theta) - 1 = 0, which gives 2cos2(θ)=12\cos^2(\theta) = 1, so cos2(θ)=12\cos^2(\theta) = \frac{1}{2}.
Then cos(θ)=±12=±22\cos(\theta) = \pm\frac{1}{\sqrt{2}} = \pm\frac{\sqrt{2}}{2}.
Thus, θ=π4+nπ2\theta = \frac{\pi}{4} + \frac{n\pi}{2}, where nn is an integer.
Combining the solutions, we have θ=nπ\theta = n\pi and θ=π4+nπ2\theta = \frac{\pi}{4} + \frac{n\pi}{2}, where nn is an integer.

3. Final Answer

The solutions are θ=nπ\theta = n\pi and θ=π4+nπ2\theta = \frac{\pi}{4} + \frac{n\pi}{2}, where nn is an integer.

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