Math Problem Statement

If θ is an acute angle and 4cosθ+4 3

sinθ=8sinθcosθ+2 3

, then which one among the following is correct? (A) sinθ= 2 3

(B) cosθ= 2 1

(C) θ=30 ∘

(D) tanθ= 3

Solution

We are given the equation involving trigonometric terms:

4cosθ+43sinθ=8sinθcosθ+234 \cos \theta + 4\sqrt{3} \sin \theta = 8 \sin \theta \cos \theta + 2\sqrt{3}

We need to determine which one of the following is correct based on the equation:

(A) sinθ=23\sin \theta = \frac{2}{3}

(B) cosθ=12\cos \theta = \frac{1}{2}

(C) θ=30\theta = 30^\circ

(D) tanθ=3\tan \theta = \sqrt{3}

Step-by-Step Solution:

  1. Simplify the given equation:

    4cosθ+43sinθ=8sinθcosθ+234 \cos \theta + 4\sqrt{3} \sin \theta = 8 \sin \theta \cos \theta + 2\sqrt{3}

    We will try to move all the terms involving θ\theta on one side and the constants on the other side.

  2. Rearrange the equation:

    Move all terms involving θ\theta to the left-hand side:

    4cosθ+43sinθ8sinθcosθ=234 \cos \theta + 4\sqrt{3} \sin \theta - 8 \sin \theta \cos \theta = 2\sqrt{3}

  3. Substitute potential values:

    Let's test each option.

    • Option B: cosθ=12\cos \theta = \frac{1}{2}

      If cosθ=12\cos \theta = \frac{1}{2}, then θ=60\theta = 60^\circ.

      We know:

      sin60=32,cos60=12\sin 60^\circ = \frac{\sqrt{3}}{2}, \quad \cos 60^\circ = \frac{1}{2}

      Substitute these values into the original equation:

      4×12+43×32=8×32×12+234 \times \frac{1}{2} + 4\sqrt{3} \times \frac{\sqrt{3}}{2} = 8 \times \frac{\sqrt{3}}{2} \times \frac{1}{2} + 2\sqrt{3}

      Simplifying:

      2+4×3=43+232 + 4 \times 3 = 4\sqrt{3} + 2\sqrt{3}

      2+12=632 + 12 = 6\sqrt{3}

      But this is not a valid identity. So, Option B is incorrect.

    • Option D: tanθ=3\tan \theta = \sqrt{3}

      If tanθ=3\tan \theta = \sqrt{3}, then θ=60\theta = 60^\circ, which is the same as tested in Option B, and that doesn't work either.

    • Option C: θ=30\theta = 30^\circ

      If θ=30\theta = 30^\circ, then:

      sin30=12,cos30=32\sin 30^\circ = \frac{1}{2}, \quad \cos 30^\circ = \frac{\sqrt{3}}{2}

      Substituting these values into the equation:

      4×32+43×12=8×12×32+234 \times \frac{\sqrt{3}}{2} + 4\sqrt{3} \times \frac{1}{2} = 8 \times \frac{1}{2} \times \frac{\sqrt{3}}{2} + 2\sqrt{3}

      Simplifying:

      23+23=23+232\sqrt{3} + 2\sqrt{3} = 2\sqrt{3} + 2\sqrt{3}

      This is a valid identity. Hence, Option C is correct: θ=30\theta = 30^\circ.

Thus, the correct answer is:

θ=30\boxed{\theta = 30^\circ}


Would you like further details or have any questions? Here are some related questions:

  1. What are the values of sin\sin, cos\cos, and tan\tan for common angles like 3030^\circ, 4545^\circ, and 6060^\circ?
  2. How can you derive the trigonometric identities used in this problem?
  3. What is the relationship between sin\sin and cos\cos for complementary angles?
  4. How can you solve more complex trigonometric equations?
  5. What are some common mistakes to avoid when solving trigonometric identities?

Tip: When solving trigonometric equations, always check for multiple possible solutions within the given range, especially if the problem involves acute angles or a restricted domain.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Trigonometric identities
Acute angles

Formulas

cosθ + sinθ identities
tanθ = sinθ/cosθ
sin 30° = 1/2
cos 30° = √3/2

Theorems

Trigonometric identity simplification
Basic angle values in trigonometry

Suitable Grade Level

Grades 10-12