Math Problem Statement

ABC is a right-angled triangle at B where 3 * AC = 5 * BC, then tan A = ?

Solution

The problem states that ABC\triangle ABC is a right-angled triangle at BB where 3AC=5BC3 \cdot AC = 5 \cdot BC. We need to find tanA\tan A.

Step-by-Step Solution:

  1. Assign the lengths: Since ABC\triangle ABC is right-angled at BB, we can apply the Pythagorean theorem. Let:

    • AC=hAC = h (hypotenuse),
    • BC=bBC = b (adjacent side to A\angle A),
    • AB=aAB = a (opposite side to A\angle A).
  2. Given Ratio: We are given 3AC=5BC3 \cdot AC = 5 \cdot BC, which simplifies to: ACBC=53\frac{AC}{BC} = \frac{5}{3} This implies that hb=53\frac{h}{b} = \frac{5}{3}, so we can assume h=5kh = 5k and b=3kb = 3k for some constant kk.

  3. Using the Pythagorean Theorem: In a right triangle, AC2=AB2+BC2AC^2 = AB^2 + BC^2. Substituting h=5kh = 5k and b=3kb = 3k: (5k)2=a2+(3k)2(5k)^2 = a^2 + (3k)^2 25k2=a2+9k225k^2 = a^2 + 9k^2 a2=25k29k2=16k2a^2 = 25k^2 - 9k^2 = 16k^2 a=4ka = 4k

  4. Finding tanA\tan A: By definition, tanA=ABBC=ab\tan A = \frac{AB}{BC} = \frac{a}{b}. Substituting the values of aa and bb: tanA=4k3k=43\tan A = \frac{4k}{3k} = \frac{4}{3}

Answer:

The value of tanA\tan A is 43\frac{4}{3}.

Thus, the correct option is: (d) 43\frac{4}{3}

Would you like more details on any of these steps?


Here are some related questions to expand your understanding:

  1. How would the answer change if the ratio 3AC=4BC3 \cdot AC = 4 \cdot BC were given instead?
  2. How is the tangent ratio related to the angle in right-angled triangles?
  3. What would be the value of sinA\sin A and cosA\cos A for this triangle?
  4. How can the Pythagorean Theorem be derived from the properties of similar triangles?
  5. How do the trigonometric ratios change as the angle AA approaches 9090^\circ or 00^\circ?

Tip: When dealing with right triangles, assigning a variable (like kk) based on the ratio can simplify calculations.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Ratios
Right-angled Triangles

Formulas

tan A = Opposite / Adjacent

Theorems

Pythagorean Theorem

Suitable Grade Level

Grades 9-10