Question

2tan(inv)a + 2 tan(inv)b = 2tan(inv)x ..
(A) (1-b)/1-ab
(B) (1+ab)/a-b
(C) ab-1/a+b
(D) a-b/1+ab

Answer 1

u want the value of x?

Answer 2

yes brother

Answer 3

simply apply the formula

Answer 4

ill try

Answer 5

i got it thanx

Answer 6

what i am getting is: (a+b)/(1-ab)

Answer 7

@ishaan

Answer 8

i am sorry , there is actually a minus sign not plus sign

Answer 9

answer is d

Answer 10

oh.. then D is correct.. it was making me confused..

Answer 11

check the questions and the options once again correctly. the "signs'. should be tan.invA "-" tan.invB. then the answer could be D

Answer 12

now i read the comments.

Answer 13

first divide both sides by 2 to have
\[\tan^{-1}a+\tan^{-1}b=\tan^{-1}x\]
then get the tan of both sides to
\[\tan(\tan^{-1}a+\tan^{-1}b)=\tan(\tan^{-1}x)\]
\[\tan(\tan^{-1}a+\tan^{-1}b)=x\]
then using the trigonometric angle sum identities:
\[\tan(a+b)=(\tan a+\tan b)/(1-tana tanb)\]
we find x,
so the LHS now becomes
\[(\tan(\tan^{-1}a)+\tan(\tan^{-1}b))/(1-\tan(\tan^{-1}a)\tan(\tan^{-1}b))\]
\[x=(a+b)/(1-ab))\]
so I have to agree with @apoorvk
this will be the answer IF: 2tan(inv)a + 2 tan(inv)b = 2tan(inv)x
D will be the answer IF:2tan(inv)a - 2 tan(inv)b = 2tan(inv)x