# How do you write 3[(cos(pi/10) + i sin (pi/10)] in rectangular form?

In rectangular form of a complex number, with real part x and imaginary part y, we use the ordered pair (x, y) to represent the complex number x + i y. Converting to polar coordinates,, using $x = r \cos \left(\theta\right) \mathmr{and} y = r \sin \left(\theta\right)$,, it becomes (r, theta) = r ( cos(theta) + i sin(theta)). Here, r = 3 and theta = pi/10 = 18 deg