How to switch tab using a button on another page in Ionic2?

I'm not sure how to open the tab2Root, using a button from my help.html page. I'm reading the docs, but there's nothing about that.

help.html:

<button ion-button large clear icon-end color="primary">
    Shop <ion-icon name="arrow-forward"></ion-icon>
</button>

tabs.html:

<ion-tabs>
    <ion-tab [root]="tab1Root" tabTitle="Home" tabIcon="home"></ion-tab>
    <ion-tab [root]="tab2Root" tabTitle="Products" tabIcon="search"></ion-tab>
    <ion-tab [root]="tab3Root" tabTitle="Cart" tabIcon="cart"></ion-tab>
    <ion-tab [root]="tab4Root" tabTitle="Account" tabIcon="person"></ion-tab>
    <ion-tab [root]="tab5Root" tabTitle="Help" tabIcon="help-buoy"></ion-tab>
</ion-tabs>