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If in a Delta ABC, sin ^(3) A + sin ^(3)...

If in a `Delta ABC, sin ^(3) A + sin ^(3) B+ sin ^(3) C`
`=3 sin A .Sin B. sin C,` then find the valueof determinant
`|{:(a,b,c),(b,c,a),(c,a,b):}|.`

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The correct Answer is:
To solve the problem, we need to find the value of the determinant given the condition involving the sine of the angles in triangle ABC. ### Step-by-Step Solution: 1. **Understanding the Given Condition:** We are given that: \[ \sin^3 A + \sin^3 B + \sin^3 C = 3 \sin A \sin B \sin C \] This condition is satisfied when \( A + B + C = 180^\circ \) (the angles of a triangle). 2. **Using the Sine Rule:** According to the sine rule in a triangle: \[ \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C} = k \] Thus, we can express the sides \( a, b, c \) in terms of \( k \): \[ a = k \sin A, \quad b = k \sin B, \quad c = k \sin C \] 3. **Substituting into the Given Condition:** Substitute \( a, b, c \) into the given condition: \[ \left(\frac{a}{k}\right)^3 + \left(\frac{b}{k}\right)^3 + \left(\frac{c}{k}\right)^3 = 3 \left(\frac{a}{k}\right) \left(\frac{b}{k}\right) \left(\frac{c}{k}\right) \] This simplifies to: \[ \frac{a^3 + b^3 + c^3}{k^3} = \frac{3abc}{k^3} \] Therefore, we have: \[ a^3 + b^3 + c^3 = 3abc \] 4. **Using the Identity:** The identity \( a^3 + b^3 + c^3 - 3abc = (a + b + c)(a^2 + b^2 + c^2 - ab - ac - bc) \) implies that: \[ a^3 + b^3 + c^3 - 3abc = 0 \] This means either \( a + b + c = 0 \) or \( a^2 + b^2 + c^2 - ab - ac - bc = 0 \). Since \( a, b, c \) are lengths of sides of a triangle, \( a + b + c \neq 0 \). Thus: \[ a^2 + b^2 + c^2 - ab - ac - bc = 0 \] 5. **Finding the Value of the Determinant:** The determinant we need to evaluate is: \[ D = \begin{vmatrix} a & b & c \\ b & c & a \\ c & a & b \end{vmatrix} \] Expanding this determinant using the first row: \[ D = a \begin{vmatrix} c & a \\ a & b \end{vmatrix} - b \begin{vmatrix} b & a \\ c & b \end{vmatrix} + c \begin{vmatrix} b & c \\ c & a \end{vmatrix} \] Calculating each of the 2x2 determinants: \[ D = a(cb - a^2) - b(bb - ac) + c(ab - c^2) \] Simplifying this gives: \[ D = acb - a^3 - b^3 + abc - c^3 \] Combining terms, we find: \[ D = 3abc - (a^3 + b^3 + c^3) \] Since \( a^3 + b^3 + c^3 = 3abc \), we have: \[ D = 3abc - 3abc = 0 \] ### Final Answer: Thus, the value of the determinant is: \[ \boxed{0} \]
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ARIHANT MATHS ENGLISH-PROPERTIES AND SOLUTION OF TRIANGLES -Exercise (Subjective Type Questions)
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  4. If R denotes circumradius, then in DeltaABC,(b^2-c^2)/(2aR) is equal t...

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  5. In DeltaABC, A = (2pi)/(3), b -c = 3 sqrt3 cm and " area of " Delta AB...

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  6. If Delta = a^(2)-(b-c)^(2), Delta is the area of the Delta ABC then ta...

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  7. In a DeltaABC, B=90^(@), AC=h and the length of perpendicular from B t...

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  8. If in a Delta ABC, sin ^(3) A + sin ^(3) B+ sin ^(3) C =3 sin A .Sin...

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  9. In a triangle ABC, if the sides a,b,c, are roots of x^3-11 x^2+38 x-40...

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  10. If the sides a,b,c are in A.P., prove that (tan)A/2+ (tan) c/2=2/3( co...

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  11. The sides of a triangle are in A.P. and its area is (3)/(5) th of an e...

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  12. If AD, BE and CF are the medians of a Delta ABC, then evaluate (AD^(2)...

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  13. Let AD be a median of the Delta ABC. If AE and AF are medians of the t...

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  14. In DeltaABC, If x= tan((B-C)/2) tan(A/2),y= tan((C-A)/2)tan(B/2), z=...

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  15. DeltaABC is equilateral triangle of side a. P lies on AB such that A i...

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  16. The base of a triangle is divided into three equal parts. If theta(1),...

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  17. If the circumradius of a triangle is 54/sqrt1463 and the sides are in...

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  18. If the angle at the vertex of an isosceles triangle having the maximum...

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  19. In an acute angle triangle ABC, AD, BE and CF are the altitudes, then ...

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  20. Let P be the point inside that Delta ABC. Such that angle APB=angle BP...

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