find the value of cos^2 75/2 - sin^2 75/2
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Answer:
Apply the cosine double-angle identity.
cos( 2.75 )
Multiply 2 by 75 .
cos ( 150 )
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the second quadrant.
− cos ( 30 )
The exact value of
cos ( 30 ) is √ 3 /2
− √ 3/ 2
The result can be shown in multiple forms.
Exact Form:
− √ 3/ 2
Decimal Form:
−0.86602540 …
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