Question

If vector P,Q,R have magnitude 5,12,13 units and P+Q=R the angle between Pand R is

Answer 1

P=5

Q=12

R=13

as we know that

R=√(P²+Q²+2PQcosx)

where x= angle between them

R²=P²+Q²+2PQcosx

169=144+25+2*12*5cosx

48cosx=0

therefore

x=π/2 or 90

this means they are perpendicular to each other.