What is the exact value of cosine of open paren 7 pi over 8 close paren ?
A
negative the fraction with numerator square root of 2 minus square root of 2 end root and denominator 2B
negative the fraction with numerator square root of 2 plus square root of 2 end root and denominator 2C
negative the fraction with numerator square root of 2 plus square root of 2 end root and denominator 4D
negative the fraction with numerator square root of 2 minus square root of 2 end root and denominator 4