# Thread: Measure of angle D

1. ## Measure of angle D

ABCD is inscribed in circle O. If angle B is 110 and angle C is 80. What is angle D?

whatt made me confuse here is that we know that consecutive angles of a quadrilateral are supplementary but 110 + 80 is 190. It impossible now to find angle D. Please guide me on this

thanks

2. ## Re: Measure of angle D

What we know is that opposite angles of a cyclic quadrilateral are supplementary.

3. ## Re: Measure of angle D

There is no such property as mentioned: consecutive angles of a quadrilateral are supplementary.

4. ## Re: Measure of angle D

Originally Posted by ibdutt
There is no such property as mentioned: consecutive angles of a quadrilateral are supplementary.
@ibdutt, I hope that you just over looked the term cyclic.
It is certainly true that opposite angles of a cyclic quadrilateral are supplementary.

What is not true is "consecutive angles of a quadrilateral are supplementary." That is the true of a parallelogram.

5. ## Re: Measure of angle D

Thanks for your response. I stick to my response that "consecutive angles of a quadrilateral are supplementary" there can be no doubt that the opposite angles of a cyclic quadrilateral are supplementary..

6. ## Re: Measure of angle D

i know now the answer and i got it... it is 70 degrees