# viewReview day 2- identities Prove each identity. sin θ + cos θ 2 =1+ sin 2θ cos 4 θ - sin 4 θ = cos 2θ sin 2 θ = 1 2 - 1 2 cos 2θ cos 2 θ = 1 2 + 1 2 cos 2θ sin 2x - sin

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### Text of viewReview day 2- identities Prove each identity. sin θ + cos θ 2 =1+ sin 2θ cos 4 θ - sin 4 θ...

Name ___________________________ 10-15 Notes

IB Math SL

Review day 2- identities

Prove each identity.

1.

2.

3.

4.

5.

Angles greater than 90 but less than 180

6. If A is an obtuse angle in a triangle and sin A = , calculate the exact value of sin 2A.

(Total 4 marks)

7. (a)Express 2 cos2 x + sin x in terms of sin x only.

(b)Solve the equation 2 cos2 x + sin x = 2 for x in the interval 0 x , giving your answers exactly.

(Total 4 marks)

8. (a) Write the expression 3 sin2 x + 4 cos x in the form a cos2 x + b cos x + c.

(b)Hence or otherwise, solve the equation

3 sin2 x + 4 cos x 4 = 0,0 x 90.

(Total 4 marks)

9. Given that sin x = , where x is an acute angle, find the exact value of

(a) cos x;

(b) cos 2x.

(Total 6 marks)

10. Consider the trigonometric equation 2 sin2 x = 1 + cos x.

(a)Write this equation in the form f (x) = 0, where f (x) = a cos2 x + b cos x + c,and a, b, c .

(a) Factorize f (x).

(d)Solve f (x) = 0 for 0 x 360.

(Total 6 marks)

11. The following diagram shows a triangle ABC, where is 90, AB = 3, AC = 2 and is.

(a) Show that sin = .

(b) Show that sin 2 = .

(c)Find the exact value of cos 2.

(Total 6 marks)

Extra Problems-optional

Prove each identity.

1.

2.

3.(a)Consider the equation 4x2 + kx + 1 = 0. For what values of k does this equation have two equal roots?

(3)

4. Let f be the function f ( ) = 2 cos 2 + 4 cos + 3, for 360 360.

(b)Show that this function may be written as f ( ) = 4 cos2 + 4 cos + 1.

(1)

(c)Consider the equation f ( ) = 0, for 360 360.

(i)How many distinct values of cos satisfy this equation?

(ii)Find all values of which satisfy this equation.

(5)

B

C

A

3

5

9

5

4

13

5

3

1

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