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  1. If tanq = sin cos sin cos a a a a - + , then sina + cosa is
    1. ± √2 sinθ
    2. ± √2 cosθ
    3. ±
      1
      sin θ
      2
    4. ±
      1
      cos θ
      2
Correct Option: B

tan θ =
sin α - cos α
sin α + cos α

∴ 1 + tan²θ
= 1 +
(sin α - cos α)²
(sin α + cos α)²

⇒ sec² θ
=
(sin α + cos α)² + (sin α - cos α)²
(sin α + cos α)²

⇒ sec²θ =
(sin² α + cos² α) + (sin α - cos α)
(sin α + cos α)²

1
=
2
cos² θ(sin α + cos α)²

1
=
±√2
cos² θ(sin α + cos α)

⇒ sinα + cosα = ± √2 cos θ



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