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# P2 Edexcel watch

1. hey i got few questions to test ur knowledge. show all the steps. i cant do them u no. i have the answers. ill type them for and tell the person, who gets them right.

1. find values of x 0,360

7 cos x + sin x = 5

2. (a) solve sin2x = cos ^ 2 x, 0> x >360
(b) solve cos 2x = 2 sin ^2 x

3. find the smallest positive value of x for which
7 cos x - 4 sin x
takes its maximum value

4. expand (x + y) ^ 6 and find (4.01)^6

5. find the values of x for which
sin x + sin 3 x + sin 5 x = 0
2. dey r hard. wot if dey come in exam
3. working on them now
4. (Original post by f_malik)
hey i got few questions to test ur knowledge. show all the steps. i cant do them u no. i have the answers. ill type them for and tell the person, who gets them right.

1. find values of x 0,360

7 cos x + sin x = 5
Can do question 1

7 cos x + sin x = 5
7 cos x = 5 - sin x
(7 cos x)^2 = (5 - sin x)^2
49 cos^2 x = sin^2 x - 10 sin x +25
49(1 - sin^2 x) = sin^2 x - 10 sin x +25
49 - 49sin^2 x = sin^2 x - 10 sin x +25
50 sin^2 x - 10 sin x -24 = 0

sin x = 0.8 or -0.6

x = sin^-1 0.8 = 53.13 (there wil be other values too)

Is this right?
5. (Original post by f_malik)
(a) solve sin2x = cos ^ 2 x, 0> x >360
sin2x = cos^2 x
2sinxcosx = cos^x
2sinx = cos^x / cos x
2sinx = cos x
sinx / cos x = 1/2
tan x = 1/2
x = 26.6
and x = 180 + 26.6 = 206.6

should be correct... wil do the rest after the match
6. Use Rsin(A+B) ..

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