In Fig. 4.242 the measures of and are respectively

In ΔABC and ΔDEF,

⇒ ∠A = ∠E = 130°

We know that SAS similarity criterion states that if one angle of a triangle is equal to one angle of the other triangle and the sides including these angles are proportional, then the two triangles are similar.

∴ ΔABC ~ ΔEFD

Hence, ∠F = ∠B = 30°

And ∠D = ∠C = 20°