Try out some algebra.....

If x = z√(1 - y2) + y√(1 - z2), find the minimum value of (x + y + z)(x - y + z)(x + y - z)(-x + y + z).

8 Answers

1
Nikhil Kaushik ·

No!
U can take....... (sin-1 x = sin-1 z + sin-1 y)

Now, can u solve it?
But, I rather had a much simpler & algebrical solution.......
It wud be gud if u an reach the answer through Trigo. also!

19
Debotosh.. ·

oops..i messed it up between cos and sin inverse,,,sorry !

62
Lokesh Verma ·

i can think of a nice(?) solution

take x=sin A , y = sin B
multiply both sides by k to get

z=sin A cos B + sin B cos A

Which reminds me of a=bcosC + c cos B

which i can get by multiplying by 2R

so 2Rz = c = a cos B + b cos A

The Thing that we have to find is closely related to the area of a triangle.. infact the square of it

Now can someone clear the question from the table ;)

62
Lokesh Verma ·

i discussed this one with nikhil yesterday..

The question has a small error.. it is not to minimize this one but to find the value of it! [1]

1
Nikhil Kaushik ·

ya but still it has a minimum value nishant....

i think its min value = 0?

isnt it??

62
Lokesh Verma ·

are u sure nikhil?

I would not jump to that conclusion so fast..

bcos the LHS here is not exactly sin a cos B + sin B cos A

but sin a |cos B| + sin B |cos A|

so you need to think slightly more before concluding what you have ;)

62
Lokesh Verma ·

btw this questino is still open :)

106
Asish Mahapatra ·

but sir, if we fix y and z such that y=z=0 then x=0.. so the value of the expression becomes zero

(I am not saying that the min. value is not zero or zero)

Still thinking

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