Question

if cos 9a=sin a and 9a<90° , then sin(a+b) is equal to​

Answer 1

Answer:

cos9α=sinα

⇒cos9α=cos(90°−α)

⇒9α=90°−α

⇒10α=90°

⇒α=9°

Answer 2

Answer:

We have,

cos 9A=sin A

To find, the value of tan 5A=?

cos9A=sin(90−A)

[ ∴cosA=sin(90−A)]

⇒ 9A = 90° - A

⇒ 10 A = 90°

⇒ A = 90/10

= 9°

∴ 5A = 5 × 9° = 45°

The value of tan5A = tan45 = 1

∴tan45=1

Hence, the value of tan5A is "1".

Step-by-step explanation:

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