cos result incorrect

I import "math.h".

I can use the cos function, but when I execute cos(0.321139585333178)开发者_运维问答 the result is 0.948876

If I use the calculator in Mac or use a normal calculator, the result is 0.999984292347418

Can anyone help me to solve that problem?

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You're confusing degrees with radians.

cos(0.321139585333178 degrees) = 0.999984292

cos(0.321139585333178 radians) = 0.948876326

• To convert from radians to degrees, multiply by 180/π.
• To convert from degrees to radians, multiply by π/180.