i can not figure out how to write the complex number in rectangular form the question is 4(cos 5Pie/6 + i sin 5 pie/6)

Answer 1

we know cos 5π/6 = =√3/2 and sin 5π/6 = 1/2
so
4(cos 5Pie/6 + i sin 5 pie/6)
= 4(-√3/2 + i(1/2) )
= -2√3 + 2i

Answer 2

Express in the form a + bi, where a and b are real numbers.
12(cos 5𝜋/4+ i sin 5𝜋/4)