



 
Tracy, The length of AB in triangle ABD is the same as the length AB in triangle ACD. Ignore piont B entirely. Thus ACD is a right triangle (the right angle is at point D, after all). So you have a right triangle ACD, you know the length AC of the hypotenuse is 8, and the angle opposite AD is 20 degrees. Is there a trig function that involves the hypotenuse, one angle and the length of the side opposite to it? Yes, it is SINE. Cheers,  


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