Lines and Angles Test - 1

Explanation:

we know that exterior angle so formed is equal to the sum of the two interior opposite angles

 Let the two interior opposite angles be x

so

x + x = 80⁰

2x = 80⁰

x = 40⁰

Explanation:

 We know that two angles, whose sum is 90°, are called complimentary angle

let one angle be x then its complimentary angle be 8x

x + 8x = 90⁰

9x = 90⁰

x = 10⁰

its complimentary angle is 8x10 = 80⁰

Explanation:

The sum of the angles of triangle  is 180 degrees.

let the angles of triangle be a ,  b, c

we have given that one angle of a triangle is equal to the sum of the other two angles

so we have

c=a + b

a + b + c = 180

Substitute c for a +b

c + c = 180

2c = 180

c = 90

therefore the triangle is a right triangle.

Explanation:

Two angles, whose sum is 90°, are called complimentary angle

let x is a complimentary angle of (9000 – a)

x + (9000 – a) = 90⁰

x = 90⁰- (9000 – a)

x = 90⁰- 9000 + a

x = a⁰