Behemoth911,
ещё для медитации ...
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
</head>
<body>
<h1>Визначення Sтд</h1>
<form id="formInput3">
<div>T3
<select id="T33" name="t3">
<option selected="selected">0.25</option>
<option>0.4</option>
<option>0.6</option>
</select>
</div>
<div>
<label>Sj</label>
<input type="number" value="9.3" name="Sj">
</div>
<div>
<label>va</label>
<input type="number" value="38.5" name="va">
</div>
<div>
<label>L</label>
<input type="number" value="2.52" name="L">
</div>
<div>
<label>C</label>
<input type="number" value="0.838" name="C">
</div>
</form>
<button onclick="make3()">Результат Sтд</button>
<h2 id="resultF4"></h2>
<script>
function breakWay3() {
const form = document.querySelector('#formInput3');
const [Sj, va, L, C, t3] = ['Sj', 'va', 'L', 'C', 't3'].map(a => +form[a].value);
const result = Sj + va * t3 / 7.2 - L - C;
return +result.toFixed(2)
}
function make3()
{
const result = breakWay3();
const div = document.querySelector('#resultF4');
div.innerText = `Результат: ${result}`;
}
</script>
</body>
</html>