Math Problem Statement

3sin18 - 4sin³18

Solution

We can simplify the expression 3sin(18)4sin3(18)3\sin(18^\circ) - 4\sin^3(18^\circ) using trigonometric identities.

There's a well-known identity for this type of expression, related to the triple angle formula for sine:

sin(3θ)=3sin(θ)4sin3(θ)\sin(3\theta) = 3\sin(\theta) - 4\sin^3(\theta)

Setting θ=18\theta = 18^\circ, the expression becomes:

3sin(18)4sin3(18)=sin(54)3\sin(18^\circ) - 4\sin^3(18^\circ) = \sin(54^\circ)

Now, using a calculator or known values for common angles, we know that:

sin(54)=0.8090\sin(54^\circ) = 0.8090

So, the value of 3sin(18)4sin3(18)3\sin(18^\circ) - 4\sin^3(18^\circ) is approximately 0.8090.

Would you like further details on the derivation of this identity or any other clarification?

Here are 5 related questions to expand on the topic:

  1. What is the derivation of the triple angle identity for sine?
  2. How do we calculate the sine of special angles like 1818^\circ?
  3. What is the general formula for sin(3θ)\sin(3\theta) and how is it used?
  4. Can we use the same approach for other trigonometric functions, like cosine or tangent?
  5. How does this identity relate to solving trigonometric equations?

Tip: Knowing special angle values and identities like the triple angle formula can help simplify trigonometric expressions efficiently.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Sine Function
Angle Identities

Formulas

Triple Angle Identity for Sine: sin(3θ) = 3sin(θ) - 4sin³(θ)

Theorems

Triple Angle Theorem

Suitable Grade Level

Grades 10-12