Question

Two force whose resultant is 10N are papendicular to each other if one of them make an angle of 60° with the resultant calculate it's magnitude/size

Answer 1

Draw a diagram.

You have a 30-60-90 triangle, whose sides are in the ratio 1 : √3 : 2
The resultant is the hypotenuse, and you want the short side, which is 5.