Question

Help explain this to me. I really don't understand...

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Answer 1

First look at triangle BCD. It is a right triangle. BD is its hypotenuse. So, you can find the length of BD using the pythagorean theorem.

Then, you look at triangle ABD. This is also a right triangle with a 60 degree angle. You can find the side length using the trigonometric ratio of sides of right triangles