Try another version of this question Box 1: Enter your answer as a number (like 5, -3, 2.2172) or as a calculation (like 5/3, 2^3, 5+4)
Find the exact value of `cos(-(13pi)/4)`.
`cos(-(13pi)/4)=`
Do not use decimals.
Enter DNE for Does Not Exist, oo for Infinity
Decimal values are not allowed
Trig functions (sin,cos,etc.) are not allowed `-sqrt(2)/2`