Question

If ABC is an equilateral triangle then value of cos(A + 2B – 3C) is
(a) 0 (b) 1 (c) 2 (d) 3

Answer 1

Step-by-step explanation:

in above there is your answer

Answer 2

Given:

An equilateral triangle ABC.

To find:

cos(A + 2B – 3C)

Solution:

We know that all the sides of an equilateral triangle are equal

this imples all the angles will be equal too.

Therefore, LA = LB = LC ....(1)

now, we have

cos(A + 2B - 3C)

Let's replace the values with values of LA in equation 1

cos (A + 2A - 3A)

solving the above equation inside brackets we get

cos (3A - 3A)

cos (0)

looking up the value of cos(0) in trigonometric table

cos(0) = 1

Option (b) is correct as the value of cos(A + 2B - 3C) is 1.