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Mathematics 11 Online
OpenStudy (anonymous):

Find the exact value of the given expression (pic)

OpenStudy (anonymous):

OpenStudy (anonymous):

tan A - tan B = (1 + tan A tan B)tan(A - B)

OpenStudy (anonymous):

so put the values n let me knw the answer

OpenStudy (anonymous):

@aajugdar That identity doesn't help alot in this case. They key still is to find tan(A) an tan(B) which you must do either way.

OpenStudy (anonymous):

i got .0641

OpenStudy (anonymous):

okay? then?

OpenStudy (anonymous):

see,she got the answer

OpenStudy (anonymous):

is it the right answer though?

OpenStudy (mathmate):

Not really! Try not to use a calculator. Use the identity and find the actual angle in terms of pi. Only at the last step would you use the calculator (if necessary).

OpenStudy (anonymous):

i dont know how to do that though. I suck at identities and ive tried so many times

OpenStudy (mathmate):

The key is to compare tan (A - B) = (1 + tan A tan B)tan(A - B) with the given expression, and try to find what is A and what is B. After that, your answer would be simply tan(A-B).

OpenStudy (mathmate):

oops, it should read: tan (A - B) = (tan(A)-tan(B))/(1+tan(A)tan(B))

OpenStudy (anonymous):

i got 1/√3 but that isnt an answer choice

OpenStudy (mathmate):

Your answer is correct, but note that 1/sqrt(3) is the same as sqrt(3)/3. Perhaps the latter is one of the choices.

OpenStudy (anonymous):

ok that was one of the choices, thanks!

OpenStudy (anonymous):

\[\frac{ \tan \frac{ 17\pi }{12 }-\tan \frac{ \pi }{ 4 } }{ 1+\tan \frac{ 17\pi }{ 12 }\tan \frac{ \pi }{ 4 } }\] \[=\tan \left( \frac{ 17\pi }{ 12 }-\frac{ \pi }{4 } \right)=\tan \frac{ 14\pi }{12 }\] \[=\tan \frac{ 7\pi }{6 }=\tan \left( \pi+\frac{ \pi }{ 6} \right)=\tan \frac{ \pi }{6 }\] now you can the solution.

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