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In a triangle cot A cot B cot C gt 0, th...

In a triangle `cot A cot B cot C gt 0`, then the triangle is

A

acute angled

B

rt. angled

C

obtuse angled

D

none

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the condition given: \( \cot A \cot B \cot C > 0 \). This condition implies that the product of the cotangents of the angles of triangle \( ABC \) is positive. ### Step-by-Step Solution: 1. **Understanding the Condition**: - The cotangent function, \( \cot \theta \), is positive when the angle \( \theta \) is in the range \( (0, \frac{\pi}{2}) \). This means that each angle \( A \), \( B \), and \( C \) must be acute angles (less than \( 90^\circ \)). 2. **Analyzing the Angles**: - Since \( \cot A > 0 \), it implies \( A \) must be in the interval \( (0, \frac{\pi}{2}) \). - Similarly, \( \cot B > 0 \) implies \( B \) must also be in the interval \( (0, \frac{\pi}{2}) \). - Lastly, \( \cot C > 0 \) implies \( C \) must be in the interval \( (0, \frac{\pi}{2}) \). 3. **Summing the Angles**: - The sum of angles in any triangle is \( A + B + C = \pi \). - If all angles \( A \), \( B \), and \( C \) are less than \( \frac{\pi}{2} \), then their sum \( A + B + C \) must also be less than \( \frac{3\pi}{2} \), which is consistent with the triangle's angle sum property. 4. **Conclusion**: - Since all angles \( A \), \( B \), and \( C \) are in the interval \( (0, \frac{\pi}{2}) \), we conclude that triangle \( ABC \) is an **acute triangle**. ### Final Answer: The triangle is **acute**.
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Knowledge Check

  • In a triangle cot A:cot B:cot C = 30:19:6 " then " a:b:c

    A
    `5:6:7`
    B
    `6:7:5`
    C
    `7:6:5`
    D
    none
  • In a triangle ABC , sum cot A cot B=

    A
    1
    B
    `-1`
    C
    0
    D
    none
  • In a triangle ABC, if cot A + cot B + cotC =cot theta , then sin ( A - theta ) sin ( B - theta ) sin ( C - theta ) =

    A
    `sin^(3) theta`
    B
    `cos^(3) theta`
    C
    `tan^(3) theta`
    D
    `cot^(3) theta`
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