Question

1-2cos²A = ? .

Answer should be = 2sin²A-1​

Answer 1

Step-by-step explanation:

A=45

∘

then 2A=90

∘

cos2A=cos90

∘

=0

2cos

2

A−1=2cos

2

45

∘

−1

=2(

2

1

)

2

−1=1−1=0

1−sin

2

A=1−2sin

2

45

∘

=1−2×(

2

1

)

2

=1−1=0

∴cos2A=2cos

2

A−1=1−2sin

2

A.

Answer 2

Step-by-step explanation:

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