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There are different ways to perform a calculation on a dynamic basis once an Angular form is validated. Here are some general steps to follow:

1. Create a function: Define a function that takes the input values from the form and performs the desired calculation. This function should return the result of the calculation.

2. Connect the function to the form: In the component that controls the form, create a method that updates the calculation result whenever the form is changed. You can do this by subscribing to the form value changes and calling the calculation function.

3. Display the result: Add a placeholder or element to the HTML template where the calculation result will be displayed. Bind this element to a variable in your component that holds the calculation result.

4. Update the result on form changes: Whenever the form changes, update the calculation result variable and display it in the relevant element in the HTML template.

Here is an example code snippet for reference:

import { Component } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';

@Component({
  selector: 'app-form',
  templateUrl: './form.component.html',
  styleUrls: ['./form.component.css']
})
export class FormComponent {
  form: FormGroup;
  result: number;

  constructor(private fb: FormBuilder) {
    this.form = this.fb.group({
      input1: ['', Validators.required],
      input2: ['', Validators.required]
    });

    this.form.valueChanges.subscribe(() => {
      this.updateResult();
    });
  }

  updateResult() {
    const input1 = this.form.get('input1').value;
    const input2 = this.form.get('input2').value;
    this.result = input1 + input2;
  }
}

In the above example, we have a simple form with two input fields. We subscribe to the value changes of the form and call the updateResult() method, which takes the input values and calculates their sum. The result is stored in the result variable, which is bound to an element in the HTML template using interpolation. Whenever the form changes, the result is updated and displayed on the page.