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Somdev kumar

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· 1 Months ago

Explain your ans

Question:
To derive the tangent formula, the following steps are given:


(1) \(tan (A+B)=\cfrac{\cfrac{sin\ A\ cos\ B}{cos\ A\ cos\ B}+\cfrac{cos\ A\ sin\ B}{cos\ A\ cos\ B}}{\cfrac{cos\ A\ cos\ B}{cos\ A\ cos\ B}+\cfrac{sin\ A\ sin\ B}{cos\ A\ cos}}\)

(2) \(tan (A+B)=\cfrac{sin\ (A+B)}{cos\ (A+B)}\)

(3) \(tan (A+B)=\cfrac{sin\ A\ cos\ B+cos\ A\ sin\ B}{cos\ A\ cos\ B - sin\ A\ sin\ B}\)

(4) \(tan A+B=\cfrac{tan\ A+\ tan\ B}{1-tan\ A\ tan\ B}\) 

Their correct and proper sequential form to derive the formula is :

Options:
A) 2, 4, 3, 1
B) 1, 2, 3, 4
C) 1, 4, 2, 3
D) 2, 3, 1, 4
Solution:
Ans: (d)

Tangent formula is derived as follows

tan (A+B) = \(\cfrac{sin(A+B)}{cos(A+B)}\)

= \(\cfrac{sinA\ cos\ B \ +cos\ A\ sinB}{cosA\ cos\ B \ -cos\ A\ sinB}\)


= \(\cfrac{\cfrac{sin\ A\ cos\ B}{cos\ A\ cos\ B}+\cfrac{cos\ A\ sin\ B}{cos\ A\ cos\ B}}{\cfrac{cos\ A\ cos\ B}{cos\ A\ cos\ B}-\cfrac{sin\ A\ sin\ B}{cos\ A\ cosB}}\)

= \(\cfrac{tanA+tanB}{1-tan\ A\ tanB}\)

\(\therefore\) Correct and proper sequential form to derive the formula is 2, 3, 1, 4.

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