Help with Geometry Proof: Find CD in terms of AD and BD

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To find CD in terms of AD and BD, consider triangle ABC formed by connecting points A, B, and C on the circle with diameter AB. The center O of the circle is equidistant from points A and B, leading to OC = OA = (AD + BD)/2. Analyzing triangle ODC, where D is the foot of the perpendicular from C to AB, helps in deriving the relationship. Triangle ABC is scalene, indicating all sides are unequal, which affects angle ACB's properties. Understanding these relationships is crucial for completing the proof.
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I need help in how to do this proof.


A circle is given with diameter AB. pick any point C on the circle and drop a perpendicular from C to the given diameter at D. Find CD in terms of AD and BD.
 
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Connect C to A and to B. What kind of triangle is triangle ABC?
 
An easier way: Let O be the centre of the circle. Then OC = OA = (AD+BD)/2. Then look at the triangle ODC to find the answer.
 
I understand upto where you have reached but I still can't proceed from there
 
kuruman said:
Connect C to A and to B. What kind of triangle is triangle ABC?

all sides are unequal
 
What do you know about angle ACB?
 
I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks

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