cos265 expressed as a pos. acute angle is....

Question

cos265 expressed as a pos. acute angle is....

Answer 1

The corresponding acute angle of 265 (third quadrant) is 85°. Therefore,

cos 265° = ±cos 85° = ±0 .08716, from the Table.

In the third quadrant, cos θ (x/r) is negative. Therefore,

 

cos 85=-0.08716

Answer 2

Subtract 265 from 360.

 

360 - 265 = 95

 

 

Subtract 95 from 180.

 

180 - 95 = 85

 

 

The positive acute angle is 85 degrees.  Since 265 degrees is in the 3rd quadrant and cosine is negative in the 3rd quadrant, the function equivalent to cos265 is

 

-cos(85)