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If A and B are supplementary angles, then find the value of  tan⁡A+tan⁡B1−tan⁡A×tan⁡B\frac{\tan A + \tan B}{1 - \tan A \times \tan B}1−tanA×
Question

If A and B are supplementary angles, then find the value of  tanA+tanB1tanA×tanB\frac{\tan A + \tan B}{1 - \tan A \times \tan B}  ?


A.

0

B.

-1

C.

1

D.

½

Correct option is A

Given:

A and B are supplementary angles, which means A + B = 180°.

Formula Used:

We use the following identity for supplementary angles:
tan(180° - A) = -tan(A)
Also, if A and B are supplementary, then B = 180° - A.

Solution:

tanA+tanB1tanA×tanB A+B=180 A=(180B) =tan(180B)+tanB1tan(180B)×tanB =tanB+tanB1+tanB×tanB =01+tan2B =0\frac{\tan A + \tan B}{1 - \tan A \times \tan B} \\\ \\A + B = 180^\circ \\\ \\A = (180^\circ - B) \\\ \\= \frac{\tan(180^\circ - B) + \tan B}{1 - \tan(180^\circ - B) \times \tan B} \\\ \\= \frac{-\tan B + \tan B}{1 + \tan B \times \tan B} \\\ \\= \frac{0}{1 + \tan^2 B} \\\ \\= 0

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