Question

If sinαsinβ - cosαcosβ + 1 = 0, then the value of cotα tanβ is

• A. –1
• B. 0
• C. 1
• D. None

Answer 1

Answer: (A)

–1

Answer 2

Given sinα sinβ – cosα cosβ + 1 = 0

⇒ cos(α + β) = 1

⇒ sin(α + β) = 0

⇒ sinα cosβ + cosα sinβ = 0

⇒ cotα tanβ = -1