Question

Prove that cos² 25+cos² 65=1

Answer 1

Answer:

Step-by-step explanation:

sin 25° cos 65° + cos 25° sin 65°

= sin 25° cos (90-25) + cos 25° sin(90-25)

= sin 25° sin 25° + cos 25° cos 25°

= sin²25° + cos²25°

= 1 [sin²A+cos²A = 1]

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