Question

(ü)
cos 12° - sin78°​

Answer 1

Answer:

By trigonometric identity, we can say

cos (90° - θ) = sin θ

Now, just replace θ by 78°.

We get

cos (90° - 78°) = sin 78°

⇒ cos 12° = sin 78° [∵, 90° - 78° = 12°]

Now, cos 12° - sin 78° = sin 78° - sin 78°

⇒ cos 12° - sin 78° = 0

Step-by-step explanation:

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