tan^-1(1/3) + tan^-1(1/5) +tan^-1 (1/7) = tan^-1 x.find x

Question

anonymous · Answer

(tan^-1) 1/3 +1/5                         8                    4
             --------   = tan^-1         --  =      tan^-1       --
             1 -  1/15                         14                  7


tan^-1  4/7 + tna^-1 1/7  =  tan-1   4/7  +   1/7    = tan^-1 35/45 =tan-1  7/9
                                                          ---------
                                                          1      -    4/49



hence x =7/9

anonymous · Answer

thank u....how did 1 -1/15 come in 1st line??

anonymous · Answer

tan^-1 a  +  tan^-1 b      =  tan^-1   a + b
                                                         ----
                                                         1 - ab

This is the only formula I've used ..  :)

anonymous · Answer

okie...got it...tnx a lot.. :)

anonymous · Answer

can u pls help me ??

tan(1/2 cos^-1 √5/3) = ?
pls tell me which formula to use..

anonymous · Answer

now all u have to do is to convert cos into tan
how do u do tht?
now cos = b/h

and tan =p/b

use pytha. theorem and get the value for p :)

anonymous · Answer

p= 2?

anonymous · Answer

yeah u got tht right :)

anonymous · Answer

so tan(1/2 tan 2/√5)  ?

anonymous · Answer

sry....tan(1/2 tan^-1 2/√5)