construct angle ABC , if BC= 6cm, m\ABC =105° and m\BCA = 30°. write down the steps of construction. question of 7th standard
Answers
BC=6 cm, ∠C=30
o
and ∠A=105
o
We know that ΔABC,∠A+∠B+∠C=180
o
Therefore, ∠B=180
o
−(∠A+∠C)
=180
o
−(105
o
+30
o
)⇒45
o
Steps of construction:
1. Draw a line BC=6 cm.
2. Draw a ray CN making an angle of 30
o
at C.
3. Draw a ray BM making an angle of 45
o
at B.
4. Locate the point of intersection of rays CN and BM and name it as A.
5. ABC is the triangle whose similar triangle is to be ji drawn.
6. Draw any ray BX making an acute angle with BC on the side opposite to the vertex A.
Answer:
Given:
BC=6 cm, ∠C=30
o
and ∠A=105
o
We know that ΔABC,∠A+∠B+∠C=180
o
Therefore, ∠B=180
o
−(∠A+∠C)
=180
o
−(105
o
+30
o
)⇒45
o
Steps of construction:
1. Draw a line BC=6 cm.
2. Draw a ray CN making an angle of 30
o
at C.
3. Draw a ray BM making an angle of 45
o
at B.
4. Locate the point of intersection of rays CN and BM and name it as A.
5. ABC is the triangle whose similar triangle is to be drawn.
6. Draw any ray BX making an acute angle with BC on the side opposite to the vertex A.
7. Locate 3 (Greater of 2 and 3 in
3
2
) points B
1
,B
2
and B
3
on BX so that BB
1
=B
1
B
2
=B
2
B
3
.
8. Join B
3
C and draw a line through B
2
(Smaller of 2 and 3 in
3
2
) parallel to B
3
C to intersect BC at C
′
.
9. Draw a line through C
′
parallel to the line CA to intersect BA at A
′
.
10. A
′
BC
′
is the required similar triangle whose sides are times the corresponding sides of ΔABC.