Question

tan 20° + tan 40° + 3 tan 20° tan 40° is
equal to
(a) 1.3
(c)-13
(b) 3
(d) -13​

Answer 1

Answer:

we have 20+ 40 = 60

so tan 60 = tan (20+40)

= (tan 20 + tan 40)/(1- tan 20 tan 40)

or tan 60 - tan 60 tan 20 tan 40 = tan 20 + tan 40

or √3 - √3 tan 20 tan 40 = tan 20 + tan 40

or tan 20 + tan 40 + √3 tan 20 tan 40 = √3

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