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Question
Choose the correct alternative:
`(1 + cot^2"A")/(1 + tan^2"A")` = ?
Options
tan2A
sec2A
cosec2A
cot2A
Solution
cot2A
`(1 + cot^2"A")/(1 + tan^2"A")`
= `("cosec"^2"A")/("sec"^2"A")`
= `(1/("sin"^2"A"))/(1/("cos"^2"A"))`
= `("cos"^2"A")/("sin"^2"A")`
= cot2A
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