How do I find cos−1(−0.6481) {cos inverse} of MATH function in Objective-C? [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

How do I get arctan MATH function in iOS?

How do 开发者_运维技巧I find cos−1(−0.6481) {cos inverse} of MATH function in Objective-C?

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math.h is available in iPhone.

#import <math.h>

double v = acos(−0.6481);