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What is cosine of 23 degree angle?
This can be done on a graphing calculator by making sure you have your calculator in degrees mode, and then tentering the cos(23). You get an answer of 0.9205048535.
What is cos2 A?
Cos(2A) = Cos(A + A) Double Angle Indentity Cos(A+A) = Cos(A)Cos(A) - Sin(A)Sin(A) => Cos^(2)[A] - SIn^(2)[A] => Cos^(2)[A] - (1 - Cos^(2)[A] => 2Cos^(2)[A] - 1
What is this expression as the cosine of an angle cos30cos55 plus sin30sin55?
cos(30)cos(55)+sin(30)sin(55)=cos(30-55) = cos(-25)=cos(25) Note: cos(a)=cos(-a) for any angle 'a'. cos(a)cos(b)+sin(a)sin(b)=cos(a-b) for any 'a' and 'b'.
Prove that sin 90 equals cos 50sin 40- cos 40 sin 50?
Sorry, but cos(50)sin(40) - cos(40)sin(50) is -0.1736, which is not even close to sin(90) which is 1.This does not work in radians, either. Please restate your question.
What is a quadrantal angle?
A Quadrantal angle is an angle that is not in Quadrant I. Consider angle 120. You want to find cos(120) . 120 lies in quadrant II. Also, 120=180-60. So, it is enough to find cos(60) and put the proper sign. cos(60)=1/2. Cosine is negative in quadrant II, Therefore, cos(120) = -1/2.
