Question

How do I know where which choices below go into the correct blanks for number 2?

Answer 1

We have a right triangle we angles 30°, 60° and 90°.

We can draw the triangle for better:

We know that CB=20 cm, so:

`\begin{gathered} \cos 60=(1)/(2)=(AC)/(CB)=(AC)/(20) \\ AC=(20)/(2)=10 \\ \text{And for pythagoras theorem:} \\ AB^2+AC^2=CB^2 \\ AB^2+10^2=20^2 \\ AB=\sqrt[]{400-100}=\sqrt[]{300}=17.32 \\ AB=\sqrt[]{3\cdot100}=10\sqrt[]{3} \end{gathered}`

So, the short leg is 10 cm and long leg is 17.32 cm.