In the given figure, OA = 5, OB = 6, OC = 3 and OD = 10, then

1. Δ AOB ∼ Δ AOB

2. Δ AOB ∼ Δ BOC

3. Δ BOC ∼ Δ COD

4. Δ AOD ∼ Δ COB

In the given figure, the value of x is:

1. 15

2. 30

3. 36

4. 40

In triangle ABC, AD is perpendicular to side BC and AD² = BD × CD.

prove that angle BAC = 90°.