Answer:
Step-by-step explanation:
Because the cosine is a positive function from which we can deduce [tex]\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\la\la\la\la\ddddddddddddddddddddddddddddddddcleverdddddd\ffffffffffffffffffffffffffffffffffffffff\pppppppppppppppppppppppppppppppppppp\dddddd \displaystyle \Large \boldsymbol{Rule : cos(-\alpha)=cos\alpha } \\\\\\ \cos\bigg(\frac{-3\pi }{4} \bigg)=cos135=-sin45=-\frac{\sqrt{2} }{2} \\\\\\cos\bigg(\frac{5\pi }{4} \bigg)=cos225=-sin45=-\frac{\sqrt{2} }{2}[/tex] Therefore, they are equal
