Question

Prove that 2cos(45+a).cos(45-a)=1-2sin2a

Answer 1

Answer:

Step-by-step explanation:

45+A) = α

(45-A) = β

2 cos α cos β = cos ( α + β ) + cos ( α - β )

= cos (45+A+45-A) + cos (45+A-(45-A)

= cos (45+A+45-A) + cos (45+A-45+A)

= cos 90 + cos 2A

= 0 + cos 2A

= cos 2A

cos 2A = 1 - 2 sin^2 A

hence proved

hope it helps...regrads