In the circle above, chord $$\overline{AB}$$ is extended to meet the tangent $$\overline{DE}$$ at D. If $$\overline{AB} = 5$$ cm and $$\overline{DE} = 6$$ cm,find the length of $$\overline{BD}$$.
given, $$AB=5cm$$ and $$DE=6cm$$
Let $$BD=xcm$$
therefore, $$AD=(x+5)cm$$
by tangent theorem
$$DE^2$$ =Â $$AD$$ *Â $$BD$$
$$6^2$$ = $$(x+5)$$ *Â $$x$$
$$36=x^2+5x$$
$$x^2+5x-36=0$$
$$\left(x-4\right)\cdot\left(x+9\right)=0$$
$$x=4$$ and $$x=-9$$ (not possible)
Hence, $$x=4$$
$$BD=4cm$$
Create a FREE account and get: