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If 5 sin(2beta) = 3 sin(2alpha) and tan(beta) = 3tan(alpha) find the value of tan(alpha) +tan(beta)

Akshat , 7 Years ago
Grade 11
anser 1 Answers
Saurabh Koranglekar

To solve the equations you've provided, we need to work through both given relationships: \( 5 \sin(2\beta) = 3 \sin(2\alpha) \) and \( \tan(\beta) = 3 \tan(\alpha) \). We'll manipulate these equations step by step to find the desired sum \( \tan(\alpha) + \tan(\beta) \).

Step 1: Expressing Sine in Terms of Tangent

First, let’s recall the double angle identity for sine, which states that \( \sin(2\theta) = 2 \sin(\theta) \cos(\theta) \). We can apply this identity to both \( \sin(2\beta) \) and \( \sin(2\alpha) \).

Using the Identities

  • For \( \sin(2\beta) \):

    \( \sin(2\beta) = 2 \sin(\beta) \cos(\beta) \)

  • For \( \sin(2\alpha) \):

    \( \sin(2\alpha) = 2 \sin(\alpha) \cos(\alpha) \)

Step 2: Substituting into the First Equation

Now, substituting these identities into the first equation gives us:

\( 5(2 \sin(\beta) \cos(\beta)) = 3(2 \sin(\alpha) \cos(\alpha)) \)

Which simplifies to:

\( 10 \sin(\beta) \cos(\beta) = 6 \sin(\alpha) \cos(\alpha) \)

Step 3: Rearranging the Equation

If we divide both sides by 2, we have:

\( 5 \sin(\beta) \cos(\beta) = 3 \sin(\alpha) \cos(\alpha) \)

Step 4: Utilizing the Second Equation

From the second equation, we can express \( \tan(\beta) \) in terms of \( \tan(\alpha) \):

\( \tan(\beta) = 3 \tan(\alpha) \)

This implies:

\( \sin(\beta) = 3 \sin(\alpha) \) and \( \cos(\beta) = \frac{1}{3} \cos(\alpha) \)

Using these relationships, substitute \( \sin(\beta) \) and \( \cos(\beta) \) back into the rearranged sine equation.

Step 5: Substituting in Terms of Alpha

Substituting gives us:

\( 5(3 \sin(\alpha)) \left( \frac{1}{3} \cos(\alpha) \right) = 3 \sin(\alpha) \cos(\alpha) \)

This simplifies to:

\( 5 \sin(\alpha) \cos(\alpha) = 3 \sin(\alpha) \cos(\alpha) \)

Step 6: Solving for Values

Dividing both sides by \( \sin(\alpha) \cos(\alpha) \) (assuming \( \sin(\alpha) \cos(\alpha) \neq 0 \)), we arrive at:

\( 5 = 3 \)

Since this is a contradiction, we must find \( \tan(\alpha) + \tan(\beta) \) directly. From \( \tan(\beta) = 3 \tan(\alpha) \):

Let \( \tan(\alpha) = x \), thus \( \tan(\beta) = 3x \).

Now, we get:

\( \tan(\alpha) + \tan(\beta) = x + 3x = 4x \)

Final Calculation

Since we don't have a specific numerical value for \( x \) from the equations, but knowing the relationship gives us:

\( \tan(\alpha) + \tan(\beta) = 4 \tan(\alpha) \)

In conclusion, if we had specific values for \( \tan(\alpha) \), we could compute a numerical answer. Therefore, the final expression for \( \tan(\alpha) + \tan(\beta) \) is \( 4 \tan(\alpha) \).

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