Solving Trig Equations — Question 1

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Question 1

Solve the equation: 2sin⁡2(x)−3sin⁡(x)+1=02\sin^2(x) - 3\sin(x) + 1 = 0 for all x∈[0,2π]x \in [0, 2\pi].

Original worksheet page 1: question and worked solution for 1-4-001
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Question 1 - Solution

We factor the equation: 2sin⁡2(x)−3sin⁡(x)+1=0.2\sin^2(x) - 3\sin(x) + 1 = 0.

Looking for factors of 2⋅1=22 \cdot 1 = 2 that add to −3-3, we write: (2sin⁡(x)−1)(sin⁡(x)−1)=0.(2\sin(x) - 1)(\sin(x) - 1) = 0.

Setting each factor equal to zero: 2sin⁡(x)−1=0orsin⁡(x)−1=0.2\sin(x) - 1 = 0 \quad \text{or} \quad \sin(x) - 1 = 0.

sin⁡(x)=12orsin⁡(x)=1.\sin(x) = \frac{1}{2} \quad \text{or} \quad \sin(x) = 1.

Now solve for x∈[0,2π]x \in [0, 2\pi]:

sin⁡(x)=1⇒x=π2.\sin(x) = 1 \Rightarrow x = \frac{\pi}{2}.

sin⁡(x)=12⇒x=π6,5π6.\sin(x) = \frac{1}{2} \Rightarrow x = \frac{\pi}{6},\ \frac{5\pi}{6}.

Therefore, the solutions are: x=π6,5π6,π2.\boxed{x = \frac{\pi}{6},\ \frac{5\pi}{6},\ \frac{\pi}{2}}.

Original worksheet page 2: question and worked solution for 1-4-001

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