Angles

The shadow of a tower becomes x metre longer when the angle of elevation of sun changes from 60° to θ. If the height of the tower is √3 x metre, then which one of the following is correct?

What is angle θ such that z is purely real? nπ ( 2 n + 1 )π

 What is angle θ such that z is purely imaginary? 

For the next two (02) items:( From 79Q to 80Q)

The angles A, B and C of a triangle ABC are in the ratio 3 : 5 : 4. 

What is the value of a + b + √2c  equal to?