title: I have a problem with angular 9 mat-tab-group
body: <p>I have a problem with angular material tabs,
  my project is angular 9.
  I created child module named it account
  inside it I created component named account-layout</p>
  
  <p>this is account-layout.component.html</p>
  
  <pre><code>    &lt;div style="padding-top: 64px;"&gt;
      &lt;p&gt;account-layout works&lt;/p&gt;
      &lt;mat-tab-group&gt;
          &lt;mat-tab label="First"&gt; Content 1 &lt;/mat-tab&gt;
          &lt;mat-tab label="Second"&gt; Content 2 &lt;/mat-tab&gt;
          &lt;mat-tab label="Third"&gt; Content 3 &lt;/mat-tab&gt;
      &lt;/mat-tab-group&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and this account-layout.component.ts</p>
  
  <pre><code>    import { Component, OnInit } from '@angular/core';
  
  @Component({
    selector: 'app-account-layout',
    templateUrl: './account-layout.component.html',
    styleUrls: ['./account-layout.component.scss']
  })
  export class AccountLayoutComponent implements OnInit {
  
    constructor() { }
  
    ngOnInit(): void {
    }
  
  }
  </code></pre>
  
  <p>and this is account.module.ts</p>
  
  <pre><code>    import { NgModule } from '@angular/core';
      import { CommonModule } from '@angular/common';
      import { AccountLayoutComponent } from './account-layout/account-layout.component';
      import { BrowserModule } from '@angular/platform-browser';
      import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
      import { MatTabsModule } from '@angular/material/tabs';
  
  
  
  @NgModule({
    imports: [
      CommonModule,
      BrowserModule,
      BrowserAnimationsModule,
      MatTabsModule
    ],
  
  
    declarations: [
      AccountLayoutComponent
    ],
  })
  export class AccountModule { }
  </code></pre>
  
  <p>now , I have this error
  error NG8001: 'mat-tab-group' is not a known element:
  1. If 'mat-tab-group' is an Angular component, then verify that it is part of this module.</p>
  
  <p>please help me Thanks.</p>