Triangle ABC is an isosceles right triangle with a right angle at A. Points D and E trisect side AC . What is the degree measure of angle BDE?
because ABC is an issosolies right triangle, the angles measure 90, 45 and 45 degrees
the measure of ABD=45 degrees and side AC is trisected --> the measures of ABE EBD and DBC are all 15
in triangle DEB we only know angle DBC BUT we can figure out CDB
CDB+BDE=180 because they make a line
the measure of BDE=60 degrees