Where is the sine function?

The Float trait was removed, and the methods are inherent implementations on the types now (f32, f64). That means there's a bit less typing to access math functions:

fn main() {
    let val: f32 = 3.14159;
    println!("{}", val.sin());
}

However, it's ambiguous if 3.14159.sin() refers to a 32- or 64-bit number, so you need to specify it explicitly. Above, I set the type of the variable, but you can also use a type suffix:

fn main() {
    println!("{}", 3.14159_f64.sin());
}

You can also use fully qualified syntax:

fn main() {
    println!("{}", f32::sin(3.14159));
}

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Real code should use the PI constant; I've used an inline number to avoid complicating the matter.