Question

plz tell me the ans of ques 16 .the diagram is also given below the ques​

Answer 1

in the triangle sum of the two angles is 90 so the third angle will be 180-90=90 and as we know if the sum of co interior angle is 90 so the lines are parallel in the question angle ECD and EAB both together are 90 so ECD+EAB=90 hence proved

Answer 2

Answer:

<ECA =<ECD .......... (1)

<EAC = <EAB ............ (2)

<ECA + <EAC = 90°

By equation 1 and 2

<ECD + <EAB = 90°,

<ECD + <EAC = 90°

So, all 4 angles are equal to each other.

<ECD + <EAB + <EAC + <ECA =180°

By theorm - if two lines having the sum of 180° of interior angles then the two lines are said to be parallel.

Hence , AB || CD