If 16 cot A = 12, then find the value of
- AOption (a)
5
- BOption (b)
8
- COption (c)
6
- DOption (d)
7
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Correct answer
7
Why this answer is correct
Shortcut Trick
Given: 16 cot A = 12 ⇒ cot A = 12/16 = 3/4
Expression to find: (sin A + cos A) ÷ (sin A − cos A)
Divide numerator and denominator by sin A:
⇒ (1 + cot A) ÷ (1 − cot A)
⇒ (1 + 3/4) ÷ (1 − 3/4) = (7/4) ÷ (1/4) = 7
∴ The correct answer is 7.
Alternate Method
Given:
16 cot A = 12 ⇒ cot A = 3/4
Formula Used:
Pythagoras Theorem: Hypotenuse2 = Base2 + Perpendicular2
sin A = Perpendicular ÷ Hypotenuse
cos A = Base ÷ Hypotenuse
Calculations:
⇒ cot A = Base ÷ Perpendicular = 3/4
⇒ Let Base = 3x and Perpendicular = 4x
⇒ Hypotenuse = √((3x)2 + (4x)2)
⇒ Hypotenuse = √(9x2 + 16x2) = √(25x2) = 5x
⇒ sin A = 4x ÷ 5x = 4/5
⇒ cos A = 3x ÷ 5x = 3/5
Now, substitute the values in the expression: (sin A + cos A) ÷ (sin A − cos A)
⇒ (4/5 + 3/5) ÷ (4/5 − 3/5)
⇒ (7/5) ÷ (1/5) = 7
∴ The correct answer is 7.
Additional Information
Trigonometric Definitions
In a right-angled triangle, tan A = sin A ÷ cos A = Perpendicular ÷ Base, and cot A = cos A ÷ sin A = Base ÷ Perpendicular.
Pythagorean Triples
Common integer sets satisfying Pythagoras theorem include (3, 4, 5), (5, 12, 13), (8, 15, 17) and (7, 24, 25). These combinations save critical calculation time in exams.
Key Trigonometric Identities
Basic square identities are: sin2 A + cos2 A = 1, 1 + tan2 A = sec2 A, and 1 + cot2 A = cosec2 A.



