How to return boolean values for checkbox checked and unchecked in ANGULAR Material 6

The concept i would want to get is ON selection of a checkbox i want the value to be returned as TRUE and ON de-selection of the same checkbox i want the value to be returned as False

This is my HTML code

<div class="form-group m-form__group row">
                                        <div class="col-lg-4">
                                            <mat-checkbox class="example-margin" type= checkbox value = "true" formControlName ="rti_cover" [checked] = "true">RTI</mat-checkbox>
                                        </div>
                                        <div class="col-lg-4">
                                            <mat-checkbox class="example-margin" type= checkbox value = "true" formControlName ="nildep_cover" [checked] = "true" >Nil Dep</mat-checkbox>
                                        </div>
                                    </div>