Question

3.) Simplify the expression.

cos ( u + π )
a.) cot u
b.) cos u
c.) sin u
d.) - cos u
e.) tan u

Answer 1

Option C) -cosu is correct

Therefore the simplified expression is
`cos(u+\pi)=-cosu`

Explanation:

Given expression is
`cos(u+\pi)`

To find the value of the given expression :

By using the formula
`cos(A+B)=cosAcosB-sinAsinB`

Substitute A=u and
`B=\pi` in the above formula we get

`cos(u+\pi)=cosucos\pi-sinusin\pi`

`=cosu(-1)-sinu(0)` ( here
`cos\pi=-1` and
`sin\pi=0` )

`=-cosu-0`

`=-cosu`

`cos(u+\pi)=-cosu`

Therefore option C) -cosu is correct

Therefore the simplified expression is
`cos(u+\pi)=-cosu`