Question

Using ruler and compasses only,

1. construct triangle ABC in which AB=5cm,BC=6cm and angle ABC=120º. 
2. measure angle ACB 
3. drop a perpendicular from C to cut AB produced at P. Measure CP. 
4. hence calculate area of triangle ABC to 1dp
5. calculate the radius of a circle that passes through the vertices of triangle ABC 

Answer 1

1.  
   
2. ∟ ACB =27°   ±1°
3. CP=5.2cm  ±0.1cm
4. A=½ × 5 × 5.2 = 13cm2
5.    5     = 2r
   sin 27
   ∴ r =    5      = 5.507
           2sin 27