Answer:
Only [tex]-cos20^o[/tex] is not equal to [tex]cos340^o[/tex]
Step-by-step explanation:
Trigonometric values
The cosine of an angle can be read as the projection in the x-axis of one point in a unit circle centered in the origin. The angles can be expressed in degrees, from 0 to 360 to make a full rotation.
The value of [tex]340^o[/tex] is located [tex]20^o[/tex] before completing the first rotation. Therefore it can be also expressed as [tex]cos(-20^o)[/tex]. The cosine function is even, i.e. it complies to
[tex]cosx=cos(-x)[/tex]
So [tex]cos(-20^o)=cos(20^o)[/tex]
Both quantities are positive, making the first option [tex]-cos20^o[/tex] incorrect
Summarizing only [tex]-cos20^o[/tex] is not equal to [tex]cos340^o[/tex]
