If a vector has equal rectangular components, it makes an angle with the x axis of

Explanation

The angle is given by the inverse tangent of the ratio of the y component to the x component, and when the two are equal that ratio is 1, whose inverse tangent is 45 degrees. Each component then has magnitude equal to the vector divided by the square root of 2. At 90 degrees the x component would be zero rather than equal to the y component.