math

posted by isaiah

sorry but i don't understand this one either
solve 4sin^2x+4√2 cosx-6 for all real values of x

1. Steve

don't forget your Algebra I now that you're in trig:

4sin^2x+4√2 cosx-6
4(1-cos^2x)+4√2 cosx-6
4 - 4cos^2x + 4√2 cosx - 6 = 0
4cos^2x - 4√2 cosx + 2 = 0
2cos^2x - 2√2 cosx + 1 = 0
(√2 cosx - 1)^2 = 0
cosx = 1/√2
x = 2kπ ± π/4

that last line because cos π/4 = cos -π/4 = 1/√2

Similar Questions

1. Math

I need someone to check my homework answers. I don't really know this stuff but i'm trying to do better in math this year. I didn't understand how to do some either. 1. √12 I got 2√3 2. √9a^3 I got 3a 3. √8 …
2. Math

Solve 4sin^2x + 4(squareroot of 2)cosx -6 for all real values of x.

Solve 4sin^2 x + 4sqrt(2) cos x-6 = 0 for all real values of x. My answer: (pi/4)+2(pi)k, (7pi/4) + 2(pi)k Solve 2cos^2 x-5cosx+2=0 for principal values of x. My answer: 60 and 300 degrees.
4. Pre Cal.

So I posted these...but no one answered them. Are they right?
5. Pre Cal

Solve 4sin^2 x + 4sqrt(2) cos x-6 = 0 for all real values of x. My answer: (pi/4)+2(pi)k, (7pi/4) + 2(pi)k Solve 2cos^2 x-5cosx+2=0 for principal values of x. My answer: 60 and 300 degrees
6. maths

q1) 2cos2x is f(x) -square root3 is g(x) solve f(x)-g(x)=0 to get points of intersection in x is between 0 and 180degrees q2) a) write the equation cos2x + 8cosx+9=0 in terms of cosx and show that for cosx it has equal roots q2b) show …
7. algebra 1 help

simplifying square roots 1) find volume of this prism?
8. Math

f(x)=x64-4x^2+k. Find the values of k so thath the zeros of f satisfy the specified charachteristics. a.four real zeros b.two real zeros, each of multiplicity of two c.two real zeros and two complex zeros d.four complez zeros a.I don't …
9. Math

I really need help with a quadratic question. So the problem is kx^2+[k+2]x-3=0 has roots which are real and positive. Find the possible values that k may have. The answer is -8+ √60<k<0 I get why they got -8+ √60 …
10. Math

Solve the integral from [0,pi] of x*sinx*cosx*dx I don't understand how to solve this problem because if I let u =x and du =1 and dv=sinx*cosx, I can't find v. How do you solve this?

More Similar Questions