Shortcut Trick
Assume an angle, say A = 45°, to quickly evaluate the expression.
⇒ sec245° = 2, cos245° = 1/2, sin245° = 1/2, cosec245° = 2
⇒ Expression = [(1 + 2) ÷ (1 + 1/2)] × [(1 + 1/2) ÷ (1 + 2)]
⇒ Expression = (3 ÷ 3/2) × (3/2 ÷ 3) = 2 × 1/2 = 1
From the given options, tan245° = (1)2 = 1.
∴ The correct answer is tan2 A.
Alternate Method
Given:
Expression = [(1 + sec2A) ÷ (1 + cos2A)] × [(1 + sin2A) ÷ (1 + cosec2A)]
Formula Used:
sec A = 1 / cos A, cosec A = 1 / sin A, tan A = sin A / cos A
Calculations:
⇒ First part = (1 + 1/cos2A) ÷ (1 + cos2A)
⇒ First part = [(cos2A + 1) / cos2A] ÷ (1 + cos2A) = 1 / cos2A
⇒ Second part = (1 + sin2A) ÷ (1 + 1/sin2A)
⇒ Second part = (1 + sin2A) ÷ [(sin2A + 1) / sin2A] = sin2A
⇒ Complete Expression = (1 / cos2A) × sin2A
⇒ Expression = sin2A / cos2A = tan2A
∴ The correct answer is tan2 A.
Additional Information
Reciprocal Trigonometric Identities
Functions that are inverted forms of each other: sec θ = 1 ÷ cos θ and cosec θ = 1 ÷ sin θ.
Quotient Identities
These identities relate tan and cot to sine and cosine: tan θ = sin θ ÷ cos θ and cot θ = cos θ ÷ sin θ.
Value Putting Technique
In the simplification of trigonometric expressions, substituting an angle like θ = 45° easily converts complex variables into numerals, aiding rapid elimination of wrong options.