Question

step of construction 70°​

Answer 1

use protractor to do so or

at first draw a semicircle and draw 90°. then from the place where 90 degree got take an arc from the place listen it is not on the semicircle it is at the place where the arc of 60 degree and 120 degree intersect.

from that point take an arc to 180 degree and bisect. you will get 140 degree. bisect it and you will get 70 degree.

Answer 2

Method of construction of 70° without using protractor...

1. Draw a line, mark a point A in the line and draw 90° in it. (Fig. 1)

  ⇒  Draw a semicircle of any radius with center at A. For next steps, a circle is drawn here.

  ⇒  Mark the points of intersection of the circle and the line as B and C.

  ⇒  Cut the circle by two arcs of same radius as that of the circle with center at B and C each.

  ⇒  Mark the points of intersection of the circle and the arcs as D and E each.

  ⇒  With center at D and E each, draw two arcs of same radius above the circle such that they meet each other at F.

  ⇒  Join AF. ∠AFB = ∠AFC = 90°. Mark the points where AF meets the semicircle as G.

2. Draw line AE. Mark the point of intersection of the circle and AE as H. ∠EAG = 30°. (Fig. 2)

3. Then we have to trisect ∠EAG = 30°. (Fig. 3 & 4)

For this, it is better to mark the length of AG at one end of a ruler and the entire method is as follows:

  ⇒  Take a ruler and mark the length of AG at one end of it.

  ⇒  Place the ruler at the point G in such a way that the one end of the length of AG marked in the ruler should be at the circle and the other end should be at the base line (line which passes through A, B and C).

  ⇒  Draw a line according to the ruler placed which passes through G.

  ⇒  Mark the point where one end of AG marked in the ruler meets the circle as I and that where the other end meets the line passing through E, A and H as J. Here, AG = IJ. (Fig. 3)

  ⇒  Draw a line through the point A parallel to the line passing through G, I and J which is formed by the ruler, and mark the point of intersection of the circle at top and this line as K. ∠EAK = 10°. (Fig. 4)

Now, ∠CAK = 70°

(See fig. 5)

Hence constructed!!!