<a href="#" class=""> clique aqui

<button (click)="form2 = !form2">Mudar</button>
      <input type="text" placeholder="email" *ngIf="form2">
      <input type="text" placeholder="form2 Email" *ngIf="!form2">

<button (click)="form2 = !form2">Mudar</button>
  <input type="text" placeholder="email" [hidden]="form2">
  <input type="text" placeholder="form2 Email" [hidden]="!form2">