The complete question in the attached figure
we know that
<span>The measure of the external angle is the semidifference of the arcs that it covers.
so
</span><span>m∠BED =(1/2)*[mAC-mBD]-------> solve for mBD
mBD=mAC-2</span>m∠BED
mBD=80-2*25--------> mBD=30°
the answer is
mBD=30°
we know that
<span>The measure of the external angle is the semidifference of the arcs that it covers.
so
</span><span>m∠BED =(1/2)*[mAC-mBD]-------> solve for mBD
mBD=mAC-2</span>m∠BED
mBD=80-2*25--------> mBD=30°
the answer is
mBD=30°
