Question

Can someone please help solve the attached :) it's on simultaneous equations combined with congruent triangles

Answer 1

2a + b = 180
a + b = 118

a = 64, b = 56

Explanation:

If you look at the triangle on the top right of the diagonal, there are 3 angles a, a and b. Since the 3 angles of a triangle add up to 180°

a + a + b = 180

=> 2a + b = 180.......(1)

We are given that the largest angle is 118°

The largest angle of the parallelogram is a + b. Remember that opposite angles of a parallelogram are equal and the sum of the angles add up to 360

Therefore a + b = 118 ....(2)

Given equations (1) and (2), subtract (1) from (2):

Eq (1) - Eq(2) :

2a + b - (a + b) = 180 - 118

a = 62

Substitute for a in equation (2) to get

a + b = 118

62 + b = 118

b = 118 - 62 = 56

So the two angles are a = 64° and b = 56°

Answer 2

a = 62, b = 56

Explanation:

given the largest angle is 118° , then

a + b = 118 ( subtract b from both sides )

a = 118 - b → (1)

the sum of the interior angles of a quadrilateral = 360°

the angle adjacent to a is b ( alternate angles ) , then

a + b + a + a + b + a = 360

4a + 2b = 360 → (2)

substitute a = 118 - b into (2)

4(118 - b) + 2b = 360

472 - 4b + 2b = 360

472 - 2b = 360 ( subtract 472 from both sides )

- 2b = - 112 ( divide both sides by - 2 )

b = 56

substitute b = 56 into (1)

a = 118 - 56 = 62

a = 62 and b = 56