5. (cos2 670 - sin2 23) ?What is the value of (cos? 670- sin2 230)?(5+

1.	5. (cos2 670 - sin2 23) ?What is the value of (cos? 670- sin2 230)?(5+3v2
Answer» 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 ] Like my answer if you find it useful!

5. (cos2 670 - sin2 23) ?What is the value of (cos? 670- sin2 230)?(5+3v2

Answer»

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 ]

Like my answer if you find it useful!