Question

2cos(45+a).cos(45-a)

Answer 1

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Answer 2

Answer:

cos2A

Step-by-step explanation:

2cos(45° + A) . cos(45° - A)

= cos[(45° + A) + (45° - A) ] + cos[(45° + A) - (45° - A) ]

= cos90° + cos(45° + A - 45° + A)

= cos2A