SOLUTION: Use the sum and difference identity to write the expression as the ine, cosine or tangent of an angle. cos20degreescos30degrees-cos20degreessin30degrees

Question 773336: Use the sum and difference identity to write the expression as the ine, cosine or tangent of an angle.
cos20degreescos30degrees-cos20degreessin30degrees
Answer by Edwin McCravy(20060) (Show Source): You can put this solution on YOUR website!
cos20degreescos30degrees-cos20degreessin30degrees

cos(A+B) ≡ cos(A)cos(B) - sin(A)sin(B)

Let A = 20� and B = 30�

cos(20�+30�) ≡ cos(20�)cos(30�) - sin(30�)sin(20�)

Answer: cos(50�)

[Incidentally you can type the little circle degree mark �
by holding down the ALT key while you type 248 on the keypad
at the far right of your keyboard. When you let up the ALT
key the � will appear on your screen.]

Edwin

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