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In a DeltaABC, P and Q are the mid-point...

In a `DeltaABC, P and Q` are the mid-points of `AB and AC` respectively. If O is the circumcentre of the `Delta ABC,` then the value of `(("Area of "Delta ABC)/("Area of " Delta OPQ)) cot B cot C` equal to

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To solve the problem, we need to find the value of \(\frac{\text{Area of } \Delta ABC}{\text{Area of } \Delta OPQ} \cdot \cot B \cdot \cot C\). ### Step 1: Identify the areas of the triangles 1. **Area of Triangle ABC**: The area of triangle \(ABC\) can be expressed using the formula: \[ \text{Area}_{ABC} = \frac{1}{2} \cdot AB \cdot AC \cdot \sin C \] We can also express this in terms of the circumradius \(R\): \[ \text{Area}_{ABC} = \frac{abc}{4R} \] where \(a = BC\), \(b = AC\), and \(c = AB\). 2. **Area of Triangle OPQ**: Since \(P\) and \(Q\) are midpoints of \(AB\) and \(AC\), respectively, the segment \(PQ\) is parallel to \(BC\) and half its length: \[ PQ = \frac{1}{2} BC = \frac{a}{2} \] The height from \(O\) to \(PQ\) can be calculated using the circumradius \(R\) and the angles: \[ OQ = R \cos B \] The angle \(PQO\) is \(90^\circ - C\), thus: \[ \text{Area}_{OPQ} = \frac{1}{2} \cdot PQ \cdot OQ \cdot \sin(PQO) = \frac{1}{2} \cdot \frac{a}{2} \cdot R \cos B \cdot \sin(90^\circ - C) = \frac{1}{2} \cdot \frac{a}{2} \cdot R \cos B \cdot \cos C \] Simplifying this gives: \[ \text{Area}_{OPQ} = \frac{aR}{4} \cos B \cos C \] ### Step 2: Calculate the ratio of the areas Now we can find the ratio of the areas: \[ \frac{\text{Area}_{ABC}}{\text{Area}_{OPQ}} = \frac{\frac{abc}{4R}}{\frac{aR}{4} \cos B \cos C} \] This simplifies to: \[ \frac{abc}{4R} \cdot \frac{4}{aR \cos B \cos C} = \frac{bc}{R^2 \cos B \cos C} \] ### Step 3: Multiply by \(\cot B \cot C\) Now we multiply this ratio by \(\cot B \cot C\): \[ \frac{bc}{R^2 \cos B \cos C} \cdot \cot B \cot C = \frac{bc}{R^2 \cos B \cos C} \cdot \frac{\cos B \cos C}{\sin B \sin C} = \frac{bc}{R^2 \sin B \sin C} \] ### Step 4: Final simplification Using the relationship \(R = \frac{abc}{4 \text{Area}_{ABC}}\), we can substitute and simplify: \[ \frac{bc}{\left(\frac{abc}{4 \text{Area}_{ABC}}\right)^2 \sin B \sin C} = \frac{4 \text{Area}_{ABC}^2}{a^2 \sin B \sin C} \] ### Conclusion After evaluating the above expressions, we find that: \[ \frac{\text{Area}_{ABC}}{\text{Area}_{OPQ}} \cdot \cot B \cdot \cot C = 4 \] Thus, the final answer is: \[ \boxed{4} \]
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