<p>In $\Delta ABC$, $AB=16$ cm, $BC=12$ cm and $AC=20$ cm.  </p>
<p>$BA$ is produced to $D$ and $AD=8$ cm.</p>
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<ol class="i-list"><li><div class="list-item-paragraph">Explain why $\angle ABC$ is a right angle.</div></li><li><div class="list-item-paragraph">Find the area of $\Delta DAC$.</div></li><li><div class="list-item-paragraph">Write down the value of $\cos \angle DAC$.</div></li></ol>

In $\Delta ABC$, $AB=16$ cm, $BC=12$ cm and $AC=20$ cm.  

Explain why $\angle ABC$ is a right angle.

Write down the value of $\cos \angle DAC$.

The Geometry of Trigonometric Ratios: From Coordinate Points to Sine and Cosine

The Geometry of Trigonometric Ratios: From Coordinate Points to Sine and Cosine

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