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In any triangle ABC, if 2Delta a-b^(2)c=...

In any triangle ABC, if `2Delta a-b^(2)c=c^(3)`, (where `Delta` is the area of triangle), then which of the following is possible ?

A

B is obtuse

B

A is obtuse

C

C is obtuse

D

B is right angle

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the given equation in the context of triangle properties. The equation provided is: \[ 2\Delta a - b^2c = c^3 \] where \( \Delta \) is the area of triangle ABC, \( a \), \( b \), and \( c \) are the sides of the triangle opposite to angles A, B, and C respectively. ### Step-by-Step Solution: 1. **Rewrite the Equation**: Start with the equation: \[ 2\Delta a - b^2c = c^3 \] Rearranging gives: \[ 2\Delta a = b^2c + c^3 \] 2. **Express Area in Terms of Sides**: The area \( \Delta \) of triangle ABC can be expressed using the formula: \[ \Delta = \frac{1}{2}ab\sin C \] Substitute this into the equation: \[ 2 \left(\frac{1}{2}ab\sin C\right) a = b^2c + c^3 \] Simplifying gives: \[ a^2b\sin C = b^2c + c^3 \] 3. **Rearranging the Equation**: Rearranging the equation yields: \[ a^2b\sin C - b^2c - c^3 = 0 \] 4. **Using the Law of Cosines**: We can relate the sides and angles of the triangle using the Law of Cosines: \[ c^2 = a^2 + b^2 - 2ab\cos C \] 5. **Analyzing the Condition**: We want to determine the conditions under which this equation holds. Particularly, we need to analyze the implications of the derived equation on the angles of the triangle. 6. **Considering the Angles**: From the derived equation, we can analyze the implications for angle A, B, and C. We will particularly look for conditions that imply obtuse angles. 7. **Finding the Conditions for Obtuse Angles**: If \( a^2b\sin C = b^2c + c^3 \) holds true, we can analyze the possibility of angle A being obtuse. For angle A to be obtuse, \( \cos A < 0 \) which implies that angle A is greater than 90 degrees. 8. **Conclusion**: After analyzing the conditions, we find that the only possibility that satisfies the equation while keeping triangle properties intact is when angle A is obtuse. ### Final Answer: Thus, the answer is that angle A is obtuse.

To solve the problem, we need to analyze the given equation in the context of triangle properties. The equation provided is: \[ 2\Delta a - b^2c = c^3 \] where \( \Delta \) is the area of triangle ABC, \( a \), \( b \), and \( c \) are the sides of the triangle opposite to angles A, B, and C respectively. ### Step-by-Step Solution: ...
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