Question

what is the value of cos2 67°-sin2 13°

Answer 1

Cos² (90-67) - sin²13
Sin² 13 - sin² 13
=0

Answer 2

The given question is wrong.

However,

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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