Question

Cos 120⁰ + Cos 240⁰ what is the answer​

Answer 1

Answer:

The pic is your correct answer

Answer 2

Answer:

-1

Step-by-step explanation:

Given :

Cos 120⁰ + Cos 240⁰

To find :

The value of the given expression

Solution :

⇒ Cos 120⁰ + Cos 240⁰

writing 240 as 180 + 60

⇒ Cos 120° + Cos (180° + 60°)

We know that,

$\boxed{\mathrm{cos(180 + x) = -cosx}}$

Here, x = 60°

⇒ Cos 120⁰ - Cos 60⁰

We know that

$\boxed{\mathrm {cos120^{\circ} = -\dfrac{1}{2}\ ; \ cos60^{\circ} = \dfrac{1}{2}}}$

Substituting the values

⇒ -¹/₂ - ¹/₂

⇒ -1

Hope it helps!!