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Higher Maths Homework Help?
Solve:
3cosx + 2 = 4
2sin^2x = 1
3tan2x + 4 = 1
I know that these are trig equations and that I have to use the CAST diagram but I do not know how to actually do the question. Can someone help talk me through how I would do these questions?
3 Answers
- Ed ILv 79 years agoFavorite Answer
3 cos x + 2 = 4
3 cos x = 2
cos x = 2/3
x ≈ 0.841, 5.442
2 sin^2 x = 1
sin^2 x = 1/2
sin x = ± √2/2
x = π/4, 3π/4, 5π/4, π/4
3 tan 2x + 4 = 1
3 tan 2x = -3
tan 2x = -1
2x = 3π/4, 5π/4, 9π/4, 13π/4
x = 3π/8, 5π/8, 9π/8, 13π/8
- trueproberLv 79 years ago
Hi KillieTillDie7, better recall these again and again
If sin x = sin t
then x = npi + (-1)^n t
And if cos x = cos t
then x = 2npi +/- t
In case of tangent function, if tan x = tan t
then x = npi + t
In all the above cases n can assume any value 0,1,2,3,4,5,6,...............................
Now let us solve the problems given by you
1) 3 cos x + 2 = 4
So cos x = 2/3
x = arc cos 2/3 = 48.2 deg
In radian 48.2/180 * pi = 0.268 pi
Hence x = 2npi +/- 0.268 pi
2) sin x = 1/,/2 = sin pi/4
So x = npi + (-1)^n pi/4
3) tan 2x = -1
or tan 2x = - tan pi/4 = tan (-pi/4)
So 2x = npi + (-pi/4)
Or x = 1/2 ( npi -pi/4) = (4n-1) *pi/8