GCSE circle theorem help please

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Can anyone help me and DS? We know we need to show that angle ACD is 90 (or ABD) but can’t work out how.

Can't quite read your picture, but you should be able to work out the angles in the 4 triangles. The intersection in the quadrilateral creates matching opposite angles

Thank you- we've got the matching opposite angles at the intersection, and opposite angles in the quadrilateral adding to 180. There just doesn't seem to be enough information to get either of the angles we need. Feel I must be missing something.

I think you need to put a letter in there. I used y

Oh my goodness thank you so much! I’ve been looking at it for hours 😂

It's badly laid out sorry

Angles in the same segment to put both letter y in.

Sorry I'm a bit braindead but you know quite a few of the angles, and the intersection ones will add up to 360 (2x +2y =360, x+y =180)

The angles of the quad add up to 360

I'd be tempted to assume that if the triangles are in a semicircle , they'll have right angles and if quad is in a semicircle,that the opposite angles are supplementary.

but I'm not an exam adjudicator and unless you are a mathematician trying to prove a theorem you shouldn't assume anything