Try another version of this question Get help: Box 1: Enter your answer as a number (like 5, -3, 2.2172) or as a calculation (like 5/3, 2^3, 5+4)
Use the sum formula for cosine to find the exact value of `cos(285^@)`
Enter DNE for Does Not Exist, oo for Infinity
Decimal values are not allowed
Trig functions (sin,cos,etc.) are not allowed `(sqrt(6)-sqrt(2))/4`