The modulus of (1) vector a+b = √ (A+B) 2 = √ (A+B) 2.

=√(a^2+b^2+2ab)=√(9+ 16+2*3*4* 1/2)=√37.

The modulus of vector a-b = √ (a-b) 2 = √ (a-b) 2.

=√(a^2+b^2-2ab)=√(9+ 16-2*3*4* 1/2)=√ 13.

(2) Cosine of the included angle @ between vector a+b and vector a-b = (A-B) * (A+B)/(| A-B || | A+B |)

=(a^2-b^2)/(|a-b||a+b|)=-7/√(37* 13).