Question

what is the value of (cos*2 67 degree - sin*2 23degree

Answer 1

(cos^2 67 degree -sin^2 23 degree)
=(cos^2  90 degree - 23 degree) - sin^2 23 degree
=(sin^2 23 degree) - ( sin^2 23 degree)
=0

Answer 2

To find:

Cos^2 67 -  Sin^2 23

Solution:

By formula,

Cos^2A - Sin^2B = Cos ( A + B ) * Cos ( A - B )

Here,

A = 67

B = 23  

Substituting,

We get,

Cos (67 + 23 ) * Cos( 67 - 23 )

Cos ( 90 ) * cos ( 45  )

Substituting values,

0 * 1/√2 .

Hence, Cos^2 67 -  Sin^2 23 = 0

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