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Stuck on IGCSE Maths Past Paper Question! watch

1. Basically I get up to figuring out that BD is 8cm but I have no idea how to get from there to finding the length of BC. I'm sure it's really obvious but I just can't figure it out! Please could someone help me out?

So far my working is:
OB/Sin30=8/Sin90
OB/Sin30=8
OB=8Sin30
OB=4
Then because OB=OD, BD=8cm

Thanks for the help!

2. "The angle in a semicircle is a right angle"
3. Maybe this will be useful.
4. (Original post by BabyMaths)
"The angle in a semicircle is a right angle"
Of course! Dammit, I knew it was something really obvious. Thank you very much!
5. <BCD is 90 degrees so just use trigonometry

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