Math Problem Statement

solve

If 13 sin A = 5, find the value of (5 sin A - 2 cos A) / tan A.

Solution

Let's solve this step-by-step:

Problem:

We are given:

13sinA=513\sin A = 5

Find the value of:

5sinA2cosAtanA\frac{5\sin A - 2\cos A}{\tan A}


Step 1: Solve for sinA\sin A and cosA\cos A:

From 13sinA=513\sin A = 5, we get:

sinA=513\sin A = \frac{5}{13}

Using the Pythagorean identity:

sin2A+cos2A=1\sin^2 A + \cos^2 A = 1

Substitute sinA=513\sin A = \frac{5}{13}:

(513)2+cos2A=1\left(\frac{5}{13}\right)^2 + \cos^2 A = 1

25169+cos2A=1\frac{25}{169} + \cos^2 A = 1

cos2A=125169=144169\cos^2 A = 1 - \frac{25}{169} = \frac{144}{169}

cosA=±1213\cos A = \pm \frac{12}{13}

Since the quadrant is not specified, we assume cosA>0\cos A > 0:

cosA=1213\cos A = \frac{12}{13}


Step 2: Solve for tanA\tan A:

tanA=sinAcosA\tan A = \frac{\sin A}{\cos A}:

tanA=5131213=512\tan A = \frac{\frac{5}{13}}{\frac{12}{13}} = \frac{5}{12}


Step 3: Evaluate 5sinA2cosAtanA\frac{5\sin A - 2\cos A}{\tan A}:

Substitute sinA=513\sin A = \frac{5}{13}, cosA=1213\cos A = \frac{12}{13}, and tanA=512\tan A = \frac{5}{12}:

The numerator is:

5sinA2cosA=5(513)2(1213)5\sin A - 2\cos A = 5\left(\frac{5}{13}\right) - 2\left(\frac{12}{13}\right)

=25132413=113= \frac{25}{13} - \frac{24}{13} = \frac{1}{13}

The denominator is tanA=512\tan A = \frac{5}{12}.

Thus:

5sinA2cosAtanA=113512=113125=1265\frac{5\sin A - 2\cos A}{\tan A} = \frac{\frac{1}{13}}{\frac{5}{12}} = \frac{1}{13} \cdot \frac{12}{5} = \frac{12}{65}


Final Answer:

1265\boxed{\frac{12}{65}}

Let me know if you have any questions or need further explanation!


Related Questions:

  1. What happens if cosA\cos A is negative?
  2. Can you solve the same problem using a different trigonometric identity?
  3. How does sinA=513\sin A = \frac{5}{13} relate to a right triangle?
  4. What is the value of cotA\cot A in this case?
  5. Can this process be generalized for any similar expression?

Tip:

Always verify the quadrant of the angle to correctly assign the signs of sin\sin, cos\cos, and tan\tan.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Pythagorean identity
Trigonometric Ratios

Formulas

sin²A + cos²A = 1
tan A = sin A / cos A

Theorems

Pythagorean Identity

Suitable Grade Level

Grades 9-11