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If in a triangle ABC , a = 6 , b = 3 and...

If in a `triangle ABC` , a = 6 , b = 3 and cos (A -B) =`4/5`,then its area in square units, is

A

4 square - unit

B

6 square - unit

C

9 square unit

D

12 square - unit

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The correct Answer is:
C
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ALLEN-Solutions of Triangle & Binomial Theorem-EXERCISE-I
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  2. The perimeter of atriangle ABC is 6 times the arihmetic mean of the si...

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  3. If in A B C ,A C is double of A B , then the value of cot(A/2).cot((B...

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  4. In Delta ABC a =5 ,b=3 ,c=7 .Then value of 3 cos C +7 cos B is equal :...

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  5. In triangle ABC, of r(1)= 2r(2)=3r(3) Then a:b is equal :-

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  6. In any Delta ABC , cot(A/2),cot(B/2),cot(C/2) are in A.P., then

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  7. In Delta ABC of a :b:c= 7 : 8: 9 .Then cos A : cos B is equal to :-

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  8. The ratio of the area of a regular polygon of n sides inscribed in a c...

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  9. In Delta ABC angle A = (pi)/(6) & b:c= 2: sqrt(3) "then " angle B is

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  10. In a triangle ABC a= 4 , b= 3 , angle A =60 ^@ ,Then c is root of equ...

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  11. In a right - angled isosceles triangle , the ratio of the circumradius...

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  12. The exradii of a triangle r(1),r(2),r(3) are in HP , then the sides a,...

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  13. Given b=2 , c= sqrt(3), angle A= 30^@ then inradius of Delta ABC is :-

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  14. In a triagnle ABC, angle B=pi/3 " and " angle C = pi/4 let D divide ...

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  15. If sin theta and - cos theta are the roots of the equation ax^2-bx-...

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  16. If A=75^0,b=45^0, then prove that b+csqrt(2)=2a

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  17. In equilateral triangle , ratio of inradius ,circum radii and exadii i...

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  18. Value of 1/(r(1)^2)'+ 1/(r(2)^2)+ 1/(r(3)^2)+ 1/(r()^2) is :

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  19. If in a triangle ABC , a = 6 , b = 3 and cos (A -B) =4/5,then its area...

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  20. If in a triangle ABC, 2 (cos A)/(a)+(cos B)/(b)+2(cos C)/(c)=(a)/(bc)+...

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