Posted by **Danny** on Tuesday, June 16, 2009 at 9:54am.

1. Use half-angle identity to find the exact value of cos165.

MY ANSWER: (-1/2)sqrt(2+sqrt(3))

2. Solve 2 sin x + sqrt(3) < 0 for 0<= x<2pi.

MY ANSWER: (4pi/3)< x < (5pi/3)

3.Write the equation 2x+ 3y-5=0 in normal form?

(-2sqrt(13)/13)x - (3sqrt(13)/13)y + 5sqrt(13)/13) = 0

- Pre Cal. -
**Reiny**, Tuesday, June 16, 2009 at 11:18am
your first one cannot be right since your result < - 1,

and the cosine and sine of any angle cannot be greater than 1 or less than -1.

there are several ways to split up 165

1. 165 = 180 - 15

2. 165 = 90 + 75, but 75 = 45 + 30

unless I misses an obvious combination, it looks like you have do this in 2 steps

third question is correct, if you follow the formula

(don't know why anybody would want to write an equation which looks very neat and clean in such a complex looking form)

## Answer this Question

## Related Questions

- Advanced Math - Can someone check these for me? Please? Use half-angle identity ...
- Calculus - Please look at my work below: Solve the initial-value problem. y'' + ...
- Precalculus check answers help! - 1. Which expression is equivalent to cos ...
- Math/Calculus - Solve the initial-value problem. Am I using the wrong value for ...
- Calculus - Second Order Differential Equations - Posted by COFFEE on Monday, ...
- Calculus - Second Order Differential Equations - Solve the initial-value problem...
- Inequality - When I solve the inquality 2x^2 - 6 < 0, I get x < + or - ...
- pre-cal - Find the roots of the function f(x)= x^2+2x+2 Determine f(x) a) (x+1-i...
- Trigonometry - If cos(a)=1/2 and sin(b)=2/3, find sin(a+b), if 1) Both angles ...
- Math Help please!! - Could someone show me how to solve these problems step by ...

More Related Questions