.triangle {
                    @include widthHeight(0);
                    @include position(absolute);
                    top: pxToRem(1);
                    left: pxToRem(73);
                    right: 0;
                    bottom: 0;
                    border-color: transparent #F0F4F8 transparent transparent;
                    border-style: solid;
                    border-width: 0.32rem 0.17rem 0 0;
                }

 <p class="us">关于我们 <i class="triangle"/> </p>