inb4 homework

const PI: f64 = 3.141592653589793238462643383279502884197169399375105820974944592307816406286;
const SMALL_ANGLE: f64 = 0.1;

enum Angle {
    Rad(f64),
    Deg(f64),
}

fn sine(angle: Angle) -> f64 {
    use Angle::{Deg, Rad};
    match angle {
        Deg(theta) => sine(Rad(theta * 2.0 * PI / 360.0)),
        Rad(theta) => if theta <= SMALL_ANGLE {
            theta
        } else {
            2.0 * sine(Rad(theta / 2.0)) * cosine(Rad(theta / 2.0))
        },
    }
}

fn cosine(angle: Angle) -> f64 {
    use Angle::{Deg, Rad};
    match angle {
        Deg(theta) => cosine(Rad(theta * 2.0 * PI / 360.0)),
        Rad(theta) => if theta <= SMALL_ANGLE {
            1.0 - theta * theta / 2.0
        } else {
            let cos_v = cosine(Rad(theta / 2.0));
            let sin_v = sine(Rad(theta / 2.0));
            cos_v * cos_v - sin_v * sin_v
        },
    }
}

fn tangent(angle: Angle) -> f64 {
    use Angle::{Deg, Rad};
    match angle {
        Deg(theta) => tangent(Rad(theta * 2.0 * PI / 360.0)),
        Rad(theta) => if theta <= SMALL_ANGLE {
            theta
        } else {
            let tan_v = tangent(Rad(theta / 2.0));
            2.0 * tan_v / (1.0 - tan_v * tan_v)
        },
    }
}

fn main() {
    println!(
        "Sin 30o: {}\nCos pi/4c: {}\nTan 45: {}",
        sine(Angle::Deg(30.0)),
        cosine(Angle::Rad(PI / 4.0)),
        tangent(Angle::Deg(45.0))
    );
}