Please help a solve a trigo sum!!
Favorites|Homepage
Subscriptions | sitemap
HOME > > Please help a solve a trigo sum!!

Please help a solve a trigo sum!!

[From: ] [author: ] [Date: 12-03-07] [Hit: ]
sin(A) = -2 ,A = 30 , 150-For equal roots ,A = 30° ,......
The quadratic eqn in x, 3X^2 - (4cosA)X + 2sinA = 0, has equal real roots.

Find the value of A, which is between 0 degrees and 360 degrees.

Appreciate it if clear workings can be shown!

-
a = 3
b = -4 * cos(A)
c = 2 * sin(A)

b^2 - 4ac = 0
16 * cos(A)^2 - 4 * 3 * 2 * sin(A) = 0
16 * cos(A)^2 - 24 * sin(A) = 0
2 * cos(A)^2 - 3 * sin(A) = 0
2 * (1 - sin(A)^2) - 3 * sin(A) = 0
-2 * sin(A)^2 - 3 * sin(A) + 2 = 0
2 * sin(A)^2 + 3 * sin(A) - 2 = 0
sin(A) = (-3 +/- sqrt(9 + 16)) / 4
sin(A) = (-3 +/- 5) / 4
sin(A) = -8/4 , 2/4
sin(A) = -2 , 1/2
sin(A) = 1/2
A = 30 , 150

-
For equal roots , b² = 4ac
16cos²A = 24sinA
2 (1 - sin²A) = 3 sinA
2 - 2sin²A = 3 sinA
2 sin²A + 3 sinA - 2 = 0
(2 sinA - 1)(sinA + 2) = 0
sinA = 1/2
A = 30° , 150°
1
keywords: solve,trigo,help,Please,sum,Please help a solve a trigo sum!!
New
Hot
© 2008-2010 http://www.science-mathematics.com . Program by zplan cms. Theme by wukong .