what is the value of sin square 69 degree minus cos squared 21 degree
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Hey there!
We know that,
cos²B - sin²A = cos(A + B) * cos ( A - B)
Now,
cos²67° - sin²23°
= cos(67 + 23 ) * cos( 67 - 23 )
= cos ( 90 ) * cos45
= 0 * 1/√2 .
= 0
cos²67 -sin²23 = 0 .
Quick Alternative : [ cos²67-sin²23 = cos²(90-23) - sin²23 = sin²23 - sin²23 = 0 ]
[ cos²67-sin²23 = cos²67-sin²(90-67) = cos²67-cos²67 = 0 ]
Hope helped!
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