Inverse Trig Question. (1 Viewer)

Fortify

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Prove:

tan^-1 (1/4) + tan^-1 (3/5) = pi/4
 

scardizzle

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Not sure if this is is right but here goes:

tan^-1 (1/4) + tan^-1 (3/5) = pi/4

if this is true then

tan(tan^-1 (1/4) + tan^-1 (3/5)) = tan pi/4 is true

RHS = (1/4 + 3/5)/(1 - 1/4 x 3/5)
= (17/20)/(17/20) = 1
= tan pi/4 = LHS
 

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