2. In the given figure, the measure of BAC is А 6 cm 2x + 20° 5 cm ° B 50° 5 cm С (a) 60° (c)70° (b)50° (d) 80°
Answers
Concept:
ⒸLTE 463)
Math 15 points
Congruence of triangles :
Two triangles are congruent, if sides and angles of a triangle are equal to
the corresponding sides and angles of the triangle. • In Congruent triangles, corresponding parts are always equal and we write it in short
'CPCT', i e, Corresponding Parts of
Congruent Triangles.
• It is necessary to write a
correspondence of vertices
correctly for writing the congruence
of triangles in symbolic form.
In AABC and AA'B'C',
AB= A'B' = 6 cm (Given)
ZB ZB¹ = 60° (Given)
BC = B'C' = 5 cm (Given)
Hence, by SAS congruence criterion, we obtain AABC = AA'B'C'.
Therefore,
ZA ZA' [By CPCT]
Now,
3x = 2x +20
3x-2x = 20°
x = 20°
Then,
ZA' = 2x +20
ZA' = 2 x 20° + 20
ZA' = 40° + 20°
ZA' = 60°
Hence, ZB'A'C' is 60°. Option (B) 60° is correct.
Answer:
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