Another interesting way to draw trendlines is the Fan principle.
When prices violate an up trendline, they will usually decline before bouncing up to test the trendline that now acts as resistance and eventually find support at a lower trendline.
Similarly, breaking the second trendline as prices are slowing down prices will decline further and bounce up to retest the previous trendline before finding support at the third trendline.

The successful violation of the third trendline signals a reversal to the downside.
Similarly, the violation of a down trendline will open the way for prices to rise before declining back to test the trendline that acts as support and then rally higher to form the second do trendline.
Subsequently, a violation of the second trendline will pull prices higher to form the third trendline.

The valid breach of the third trendline will signal the reversal to the upside.