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The Unit Circle is a circle that has a radius of 1 and a center at the origin.
If you look at the unit circle 90 degrees is at the point (0,1).
Cosine is equal to the x value of a point on the Unit Circle.
The line created to the point (0,1) on the unit circle when the degree is 90 is completely vertical, which in turn makes the x value 0 and thus, cosine of 90 = 0.
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Why does x equal 0 when finding the sin of 90 degrees?
On the unit circle sin(90) degrees is at Y = 1 and as that is on the Y axis X will equal = 0. Ask yourself. Where would 90 degrees be on a 360 degree circle? Straight up.
1 over cos y is equal to?
1/cos y = sec y
What is cos2x equal to?
You can look up "trigonometric identities" in Wikipedia.Cos(2x), among other things, is equal to (cos x)^2 - (sin x)^2 If you meant cos squared x, or (cos x)^2, that is equal to (1 + cos(2x))/2
What is the value of 1- cos x when x is small?
1 - cos x as x approaches 0. what is the cos of 0? It is 1. So as x approaches 0 cos x approaches 1. 1 - 1 = 0 So as it gets very small the solutions gets smaller.
Show that sin x equals cos x for some angle t between 0 and 90?
sin(x) = cos(x)sin(x)/cos(x) = tan(x) = 1x = arctan(1) = 45 degreessin(45)=cos(45) = Sqrt(2)/2 Answer: By observation. Since Sine = Opposite over hypotenuse and Cosine = Adjacent over hypotenuse. Any right angle triangle where the opposite and adjacent sides are the same length will have Sine equal to Cosine. This only happens with an isosceles triangle (two sides are equal in length). When one angle is 90o the other two are 45o.
