# Amaths Trigonometry (Double angle) Questions

Hi Jessie W,

( Jessie Lau, in case you are reading this, this post is not for you! hehe! I have another student by the name of Jessie this year. )

Here are the 3 questions on Trigo Double Angle!

Please attempt and complete these questions together with the homework I gave during class.

You may key your answers in the comments column below so that I can check your answers before class and save some time. 🙂

(1) Given that cos x = -0.6 and that ∏ < x < 3∏/2 , find without using calculator, the value of

(a) sin 2x

(b) tan 4x

(2) Find all the values of x between 00 and  3600 inclusive which satisfy the equation

(a) 4cos 2x – 3sin x + 1 =0

(b) 2cot 2x =5

(3) The function f is defined by f(x) = 4cos 2x-2

(a) State the amplitude of f

(b) State the period of f

The equation of a curve is y = 4cos 2x -2 for 0  < x < 1800

(c) Find the coordinates of the minimum point of the curve

(d) Find the coordinates of the points where the curve meets the x-axis

(e) Sketch the graph of y = |4cos 2x -2| for 00   < x < 1800

* Q3 is N2008/P2/Q7