Question

(cos²67 degree - sin² 23 degree) what is the value of this

Answer 1

cos²67° - sin²23°
cos²(90-67) - sin² 23°
sin²23° - sin² 23°
=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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