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# Wtf Is Dis watch

1. solve equation

arctan x + arctan 2x = pi/4
2. take tan of both sides and use tan(A +B) expansion
3. (Original post by s-man)
take tan of both sides and use tan(A +B) expansion
how do you actually solve arctan..etc equations? i know that it is the inverse function of tan..etc
4. (Original post by TheWolf)
how do you actually solve arctan..etc equations? i know that it is the inverse function of tan..etc
give me an example i dont understand wot u mean.......if arctanX=3....then X=tan3.......
5. (Original post by s-man)
give me an example i dont understand wot u mean.......if arctanX=3....then X=tan3.......
ok give arccos -0.5 in radians
6. (Original post by TheWolf)
ok give arccos -0.5 in radians

2Pi/3
7. (Original post by s-man)
2Pi/3
8. (Original post by TheWolf)
u need to kno ur basic trig values i.e. cos(pi/3) =0.5 etc and work backwards, by using a cos graph if it helps
9. whered u get such a wierd question ??? .. ive done so many papers and never come across such a problem ...

if its edexcel , usually the first part fo the question helps in solving the later ... perhaps u had to prove some identity above ....

jus use the same identity (if any ) to solve this ... other wise ... i dont think u can solve this witout using the tan ( A+B) identity
10. (Original post by f_malik)
solve equation

arctan x + arctan 2x = pi/4
wot so tan(arctanx+arctan2x)=1
(x+2x)/(1-2x^2)=1

so x+2x=1-2x^2
so 2x^2+3x-1=0
so x=(-3+/-sqrt(9+8))/4
=-0.75+-sqrt17/4
11. (Original post by s-man)
u need to kno ur basic trig values i.e. cos(pi/3) =0.5 etc and work backwards, by using a cos graph if it helps

if u want asnwer in terms of pi:
cos^-1(-0.5) /pi = 2/3

so arccors-0.5=(2/3) pi
is how i'd do it. not the best method tho.

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Updated: June 20, 2004
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