Page 170 - Start Up Mathematics_7

2. In the given figures, the measures of some angles are given. State whether the triangles are
acute, right or obtuse.

(a) (b) (c)
60° 45° 30° 60° 30°

3. In the given figure, find the measure of ∠ACD.

A

70°

50°
B
C D
4. An exterior angle of a triangle is 130° and one of the interior opposite angles is 45°. Find
the other two angles of the triangle.
5. One of the acute angles in a right triangle is 60°. Find the other acute angle.
6. If one angle of a triangle is equal to the sum of the other two, show that the triangle is
right-angled.
7. If one angle of a triangle is 60° and the other two angles are in the ratio 1 : 2, find the angles.
8. The angles of a triangle are in the ratio 1 : 2 : 3. Find them.

9. In the figures given below, find x and y.

y C
30° 80°
x
(a) (b) (c)
y x

x
A B 60° 45° 60° y
C

x
A
(d) x 30° (e)

120° y
45° 110° y 110°
B C D D A B E

Sum of the Lengths of Two Sides of a Triangle
In a triangle, sum of the lengths of any two sides is always greater than the third side. Let’s learn
it with the help of an activity.

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