How to calculation -sqrt ?

Using Arduino Programming Questions
1

Dear All,

How to write that V = -sqrt{(2 * (Pd /1000)) / 1.225} to the arduino program.

2 
V = -sqrt((2. * Pd /1000.) / 1.225);

Which is the same as

V = -sqrt(Pd*1.633E-3);
3

jremington:

V = -sqrt((2. * Pd /1000.) / 1.225);

Which is the same as

V = -sqrt(Pd*1.633E-3);

I use your code to the program, but it wrong output.

4

There may be some mistake. I rewrite that show you.

the calculation is √{(2 * (Pd /1000)) / 1.225}

5

I use your code to the program, but it wrong output.

How do you know?

Is there a minus sign "-" or not?

6

the original formula is V= √{(2 * (Pd /1000)) / 1.225}

  • sqrt = √ ?
7

shanelle:
the original formula is V= √{(2 * (Pd /1000)) / 1.225}

  • sqrt = √ ?

In math and C++, a leading minus sign indicates a negative value.

8

Without the minus sign, the formula is

V = sqrt(Pd*1.633E-3);

You need to declare V as float.

9

In the sticky thread, point 13, there's a link to the AVR libc docs. sqrt() in in the docs for math.h.

10

like this?

void setup()
{
  Serial.begin(115200);
  Serial.print("Start ");
  Serial.println(__FILE__);

  for (float Pd = 0; Pd < 10; Pd = Pd + 0.01)
  {
    float val = 2.0 * (Pd / 1000.0) / 1.225;
    float v = sqrt( val );
    Serial.print(Pd);
    Serial.print("\t");
    Serial.println(v);
  }
  
}

void loop()
{
}