-<span class="st"> </span><span class="kw">asin</span>(<span class="dv">1</span>/<span class="fl">1.5</span>) *<span class="st"> </span><span class="dv">180</span>/pi

<span class="kw">ggplot</span>(m) +<span class="st"> </span><span class="kw">geom_vline</span>(<span class="kw">aes</span>(<span class="dt">xintercept =</span> x), <span class="dt">data =</span> <span class="kw">data.frame</span>(<span class="dt">x =</span> tir), <span class="dt">linetype =</span> <span class="dv">2</span>, 
    <span class="