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What is the value of cos θ given that (-2, 9) is a point on the terminal side of θ?

What is the value of cos θ given that (-2, 9) is a point on the terminal side of θ?-example-1
User Saketh
by
8.7k points

1 Answer

4 votes

Answer:

a) cosθ =
(-2√(85) )/(85)

Explanation:

Step(i):-

Given point ( x , y ) = ( - 2 , 3 )

We know that the polar co-ordinates

x = r cos θ and y = r sinθ

where
r = \sqrt{x^(2) +y^(2) }


r = \sqrt{(-2)^(2) +(9)^(2) } = √(4+81) = √(85)

Step(ii):-

x = r cos θ

cosθ
= (x)/(r)

cosθ =
(-2)/(√(85) ) = (-2)/(√(85) ) X (√(85) )/(√(85) )

cosθ =
(-2√(85) )/(85)

User Michalbrz
by
8.0k points

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