can anyone answer this A level vectors question (very challenging)

Points A and B have position vectors a and b, respectively, relative to an origin O, and are such that OAB is a triangle with OA = a and OB = b.
the point C, with position vector c, lies on the line through O that bisects the angle AOB.
1.) prove that the vector ba-ab is perpendicular to c.
the point D, with position vector d, lies on the line AB between A and B.
2.) explain why d can be expressed in the form d=(1-λ)a+λb for some scalar λ with 0<λ<1
3.) given that D is also on the line OC, find an expression for λ in terms of a and b only and hence show that
DAB = OA:OB

What have you tried and can you upload a pic of the question? Not sure about the ba-ab in part 1)?

Edit - its question 5 in
https://qualifications.pearson.com/content/dam/pdf/Advanced%20Extension%20Award/Mathematics/2018/exam-materials/9811_01_que_20190815.pdf
So what have you tried, the first two parts should be relatively straightforward?

What have you tried and can you upload a pic of the question? Not sure about the ba-ab in part 1)?

Edit - its question 5 in
https://qualifications.pearson.com/content/dam/pdf/Advanced%20Extension%20Award/Mathematics/2018/exam-materials/9811_01_que_20190815.pdf
So what have you tried, the first two parts should be relatively straightforward?

thank you i was able to solve it, i just had a bit of difficulty recognising that it would be an isosceles triangle, and if you add 2 points such that the position of the vector from the origin was ba for one and ab for the other it is quite simple. i was also told it can be solved using dot products but not entirely sure on the method for that