The diagram illustrates the construction of the figures for all three questions.
The colours aid in the descriptions below. Mark C as the intersection of the two circles.
Q1.
Draw a (red dotted) circle centre A and draw an extended diameter where black B to green B is the diameter.
With centre at green B draw a second (red dotted) circle of the same size. Join C to black B and A. This is the required triangle. Draw the same size circle with centre green B.
Q2.
With centre at black B and radius beyond A draw a (blue dotted) circle. With centre at green B draw another (blue dotted) circle which intersects the other circle. Draw a line from the intersection cutting through red BC at blue C. This gives us the right triangle formed by A, B and blue C.
Q3.
Join red C to A and green B. The green triangle is the required one.