91Ó°ÊÓ

As the measurement of angle CBF is already given and the perpendicular relation between the given lines represents that the measurement of $∠ABE$, $∠CBE$ and$∠DBF$ is equal to 90°.

According to the figure $∠EBF$and $∠CBF$makes the right $∠EBC$so by using this determines the value of $∠EBF$.

$$\begin{gathered} ∠EBC=∠EBF+∠CBF \\ 90=∠EBF+40 \\ ∠EBF=90−40 \\ ∠EBF=50 \end{gathered}$$

According to the figure$∠EBF$and$∠DBE$makes the right$∠DBF$so by using this determine the value of .

According to the figure and makes the right so by using this determine the value of $∠DBE$.

$$\begin{gathered} ∠DBF=∠EBF+∠DBE \\ 90=50+∠DBE \\ ∠DBE=90−50 \\ ∠DBE=40 \end{gathered}$$

According to the figure $∠DBA$and $∠DBE$makes the right $∠ABE$so by using this determines the value of $∠DBA$.

$$\begin{gathered} ∠ABE=∠DBA+∠DBE \\ 90=∠DBA+40 \\ ∠DBA=90−40 \\ ∠DBA=50 \end{gathered}$$

According to the figure the right $∠DBF$and $∠CBF$makes $∠DBC$so by using this determines the value of $∠DBC$.

$$\begin{gathered} ∠DBC=∠DBF+∠CBF \\ =90+40 \\ =130 \end{gathered}$$

Make the complete table by writing the value of obtained angles into their respective columns.