(i) I start by taking the triangle AOB where AB = x and AHO & BHO

(ii)Because I'm required to prove using cot I'm going to use tan. Therefore:

tan (alpha) = h/AO

AO = h/tan (alpha)

AO = h*cot (alpha)

tan (beta) = h/BO

BO = h/tan (beta)

BO = h*cot (beta)

(iii) uisng cosine law:

x^2 = (AO)^2 + (BO)^2 - 2(AO)(BO)Cos (theta)

I try to manipluate this to equal 2x^2 but can't see the link.

Can you show me how this is proven? There are other parts to the question but I think once I understand this I will be okay on my own.

many thanks!!