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look at this diagram: diagram of two parallel vertical lines (ce and fh…

Question

look at this diagram:
diagram of two parallel vertical lines (ce and fh) cut by a transversal (bi), with points d on ce, g on fh, e above d, c below d, h above g, f below g, b left of d, i right of g
if \overleftrightarrow{ce} and \overleftrightarrow{fh} are parallel lines and m\angle cdg = 70°, what is m\angle cdb?

Explanation:

Step1: Identify Angle Relationship

Since \( \overleftrightarrow{CE} \parallel \overleftrightarrow{FH} \) and \( \overleftrightarrow{BI} \) is a transversal, \( \angle CDB \) and \( \angle CDG \) are supplementary (they form a linear pair, or consecutive interior angles? Wait, actually, \( \angle CDB \) and \( \angle CDG \) are adjacent and form a straight line? Wait, no, \( \angle CDG = 70^\circ \), and \( \angle CDB \) and \( \angle CDG \) are supplementary because they are adjacent angles on a straight line (linear pair). Wait, no, looking at the diagram: \( D \) is on \( CE \), \( G \) is on \( FH \), and \( BI \) is a transversal. Wait, actually, \( \angle CDB \) and \( \angle HGD \) would be corresponding, but no—wait, \( \angle CDG \) is given as \( 70^\circ \), and \( \angle CDB \) and \( \angle CDG \) are supplementary because they are adjacent and form a linear pair (they add up to \( 180^\circ \))? Wait, no, maybe I misread. Wait, the problem says \( m\angle CDG = 70^\circ \), and we need \( m\angle CDB \). Wait, \( D \) is the intersection of \( BI \) and \( CE \), \( G \) is the intersection of \( BI \) and \( FH \). Since \( CE \parallel FH \), \( \angle CDB \) and \( \angle HGI \) or something? Wait, no, let's think again. The straight line \( BI \) intersects \( CE \) at \( D \) and \( FH \) at \( G \). So \( \angle CDB \) and \( \angle CDG \) are adjacent angles forming a linear pair, so they should add up to \( 180^\circ \). Wait, that makes sense. So if \( m\angle CDG = 70^\circ \), then \( m\angle CDB = 180^\circ - 70^\circ = 110^\circ \)? Wait, no, maybe I got the angles wrong. Wait, \( \angle CDB \) and \( \angle CDG \): let's label the points. \( CE \) is a vertical line (up and down), \( FH \) is parallel to \( CE \). \( BI \) is a transversal going from \( B \) (left) through \( D \) (on \( CE \)) to \( G \) (on \( FH \)) to \( I \) (right). So \( \angle CDG \) is the angle at \( D \) between \( CD \) (down along \( CE \)) and \( DG \) (right along \( BI \)). \( \angle CDB \) is the angle at \( D \) between \( CD \) (down along \( CE \)) and \( DB \) (left along \( BI \)). So \( \angle CDB \) and \( \angle CDG \) are adjacent and form a linear pair, so they are supplementary. Therefore, \( m\angle CDB + m\angle CDG = 180^\circ \). So \( m\angle CDB = 180^\circ - 70^\circ = 110^\circ \). Wait, but maybe they are alternate interior angles? No, because \( CE \parallel FH \), and \( BI \) is a transversal. Wait, no, \( D \) is on \( CE \), \( G \) is on \( FH \). So \( \angle CDB \) and \( \angle HGD \) would be corresponding angles, but \( \angle CDG \) is \( 70^\circ \), so \( \angle HGD = 70^\circ \) (vertical angles or corresponding). Then \( \angle CDB \) would be supplementary to \( \angle HGD \) because \( CE \parallel FH \), so consecutive interior angles? Wait, maybe I confused the angles. Let's start over.

Step1: Recognize Linear Pair

\( \angle CDB \) and \( \angle CDG \) form a linear pair (they are adjacent angles on a straight line \( BI \)), so their measures sum to \( 180^\circ \).

Step2: Calculate \( m\angle CDB \)

Given \( m\angle CDG = 70^\circ \), we use the linear pair property:
\( m\angle CDB + m\angle CDG = 180^\circ \)
Substitute \( m\angle CDG = 70^\circ \):
\( m\angle CDB = 180^\circ - 70^\circ = 110^\circ \)

Answer:

\( 110^\circ \)