Question

Find the value of cos(-90).

Answer 1

We know,

`\cos (-\theta)=\cos \theta`

Therefore,

`\cos (-90^(\circ))=\cos 90^(\circ)`

We also know,

`\cos 90^(\circ)=0`

Hence,

`\begin{gathered} \cos (-90^(\circ))=\cos 90^(\circ)=0 \\ \cos (-90^(\circ))=0 \end{gathered}`

So, the value of cos(-90) is zero.