Question-193669

Question Number 193669 by Rupesh123 last updated on 17/Jun/23

Answered by AST last updated on 18/Jun/23

c o s (x + y) + i s i n (x + y) = e^{i (x + y)} = e^{i x} e^{i y}

= (c o s (x) + i s i n (x)) (c o s (y) + i s i n (y))

= c o s (x) c o s (y) - s i n (x) c o s (y) + i c o s (x) s i n (y) + i s i n (x) c o s (y)

C o m p a r i n g r e a l p a r t s

\Rightarrow c o s (x + y) = c o s (x) c o s (y) - s i n (x) c o s (y)

Commented by Rupesh123 last updated on 18/Jun/23

Perfect ��