如何在java中编写sin平方

Question

double maxHeight = 0.0;

velocity = v;
angle = theta;

maxHeight = Math.pow(velocity, 2.0);
maxHeight = Math.pow(sin, 2.0);
maxHeight *= Math.sin(angle) / (2 * gravity);

I'm trying to get the Math.pow(sin, 2.0); . it's asking me to declare sin . What am I supposed to put down for it? I'm just trying to get sin squared.

Answer 1

First of all - Math.pow(x, 2.0) is equal to sin * sin, and the second approach should be much more efficient.

When it comes to answer to your question - does the variable "sin" you want to use in second Math.pow() exists?

Example code:

// assuming that "v", "theta" and "gravity" are known variables

double sin = Math.sin(theta);
double maxHeight = (v * v * sin * sin) / (gravity * 2);

Corrected original code:

double maxHeight = 0.0;

velocity = v;
angle = theta;

maxHeight = Math.pow(velocity, 2.0);
double sin = Math.sin(angle);
maxHeight *= Math.pow(sin, 2.0) / (2 * gravity);

Answer 2

The problem with your current code is that you are trying to access a variable named sin but that variable doesn't exist. Since you're starting with Java, let's start over.

You want to calculate h = v² sin²( θ ) / ( 2 g ) . We already have v and theta .

First, the numerator is v² sin²(θ) . This means we need to calculate v² . Then we need to calculate sin(θ) and square the result. Then we need to multiply those two number together. Put to code, we have:

double vSquared = Math.pow(v, 2);
double sinTheta = Math.sin(theta);
double sinThetaSquared = Math.pow(sinTheta, 2);
double numerator = vSquared * sinThetaSquared;

The denominator is simply 2*g so we have:

double maxHeight = numerator / (2 * gravity);

If we simplify this into a single expression, we come up with:

//test data
double v = 1.0;
double theta = 1.5;
double gravity = 9.8;

double maxHeight = Math.pow(v, 2) * Math.pow(Math.sin(theta), 2) / (2 * gravity);