Question

Evaluate cos 150° without using a calculator.Ο Α.√32B. 2O C. -1/2OD. -32

Answer 1

Answer:

Step-by-step explanation:

Note that:

`\begin{gathered} cos(A+B)=cosAcosB-sinAsinB \\ cos(150^0)=cos(90+60) \end{gathered}`

Applying the addition formula given above to cos 150:

`\begin{gathered} cos(150)=cos(90)cos(60)-sin(90)sin(60) \\ \\ cos(150)=0((1)/(2))-1((√(3))/(2)) \\ \\ cos(150)=0-(√(3))/(2) \\ \\ cos \end{gathered}`