\operatorname { cos } \frac { 5 \pi } { 3 } + \operatorname { cos } 4

1.	\operatorname { cos } \frac { 5 \pi } { 3 } + \operatorname { cos } 4 \frac { 4 \pi } { 3 } + \operatorname { sin } \frac { 3 \pi } { 2 } \times \operatorname { sin } \frac { 5 \pi } { 8 } \times \operatorname { cos } 3 \pi
Answer» cos(5π/3) + cos(4π/3) + sin(3π/2)×sin(5π/8)×cos(3π/2) = 1/2 + (-1/2) + -1(sin5π/8)0= 1/2-1/2 +0= 0

\operatorname { cos } \frac { 5 \pi } { 3 } + \operatorname { cos } 4 \frac { 4 \pi } { 3 } + \operatorname { sin } \frac { 3 \pi } { 2 } \times \operatorname { sin } \frac { 5 \pi } { 8 } \times \operatorname { cos } 3 \pi

Answer»

cos(5π/3) + cos(4π/3) + sin(3π/2)×sin(5π/8)×cos(3π/2)

= 1/2 + (-1/2) + -1*(sin5π/8)*0= 1/2-1/2 +0= 0