Question

find the value of cos 135° - sin 225°

Answer 1

0 is the right answer

Answer 2

cos 135 = cos (180-45)
= -cos 45

$\frac{ - 1}{ \sqrt{2} }$

sin 225 = sin(180+45)
= - sin 45

$\frac{ - 1}{ \sqrt{2} }$

Therefore, cos 135 - sin 225 =

$\frac{ - 1}{ \sqrt{2} } - \frac{ - 1}{ \sqrt{2} } = 0$