i don't understand why the related acute angle of cos 3pie/4 is cos 5pie/4. i thought u use formula like 180 - 135= 45 (since it's in 2nd quadrant), so shouldn't it be pie/4 instead of cos 5pie/4??
please explain it in detail thank you
it doesn't say cos negative quadrant. just cos 3pie/4
please explain it in detail thank you
it doesn't say cos negative quadrant. just cos 3pie/4