Seems like I can only work it out if I assume that lineCD is perpendicular to lineAB. I'm not sure I need to know that they're congruent, so maybe it's a typo?
this post was submitted on 17 Apr 2025
3 points (100.0% liked)
ask_math
68 readers
3 users here now
A community to ask math questions with the goal of learning math.
When you ask a question, include a description of what you have already tried and where you feel you are stuck.
When answering a question, avoid simply giving the answer.
Let’s not do other people’s homework for them.
Similar communities: For general math news and conversation: https://lemmy.world/c/math
founded 2 years ago
MODERATORS
It's been a long time since I've done this, and as I recall they'd mark if angle ADC right, and not let you assume it to be so just because it happens to be drawn so.
For a general solution you could probably use the paw of cosines on triangles ABC and ADC to create two equations for angle CAD in terms of x and y, where y = AD, then solve them. Feels like a rather brutish method though, and I don't know how pleasant those equations would be, and ugly calculations tend to be a bad sign.
There's no way that this involves cosines. I'm making of note that it looks like a typo on the answer and solving it that way.