Home » Aptitude » Trigonometry » Question
  1. If
    cos α
    = a,
    sin α
    = b, then sin²β is equal to
    cosβsinβ
    1. a² - 1
      a² + b²
    2. a² + 1
      a² - b²
    3. a² - 1
      a² - b²
    4. a² + 1
      a² + b²
Correct Option: C

cosα
= a
cosβ

cos²α
= a²
cos²β

1 - sin²α
= a²
1 - sin²β

⇒ 1 – sin²α = α² (1 – sin²β)
⇒1 – b² sin²β = a² – a² sin²β
⇒ 1 – a² = b ²sin²β – a² sin²β
⇒ 1 – a² = (b² – a² ) sin²β
⇒ sin²β =
1 - a²
=
a² - 1
b² - a²a² - b²



Your comments will be displayed only after manual approval.