Trigonometric functions and their reciprocals on the unit circle. All of the right-angled triangles are similar, i.e. the ratios between their corresponding sides are the same. For sin, cos and tan the unit-length radius forms the hypotenuse of the triangle that defines them.

\(\begin{array}{l}\sin\: x\cdot \cos\:y=\frac{\sin(x+y)+\sin(x-y)}{2}\end{array} \)

A basic trigonometric equation has the form sin(x)=a, cos(x)=a, tan(x)=a, cot(x)=a

2024年12月16日 · cos x + cos y formula; 2 sin x sin y formula Finding Principal solutions; Finding General Solutions; Sine and Cosine Formula

sin(2x) = 2 sin x cos x cos(2x) = cos ^2 (x) - sin ^2 (x) = 2 cos ^2 (x) - 1 = 1 - 2 sin ^2 (x) tan(2x) = 2 tan(x) / (1 - tan ^2 (x))

2017年8月6日 · $$\sin(x+y) =\sin(x)\cos(y) + \cos(x)\sin(y)$$ consist of drawing a couple of triangles, one on top of each other and then figuring out some angles and lengths until they arrive at the identity.

You can see the Pythagorean-Thereom relationship clearly if you consider the unit circle, where the angle is t, the "opposite" side is sin(t) = y, the "adjacent" side is cos(t) = x, and the hypotenuse is 1. We have additional identities related to the functional status of the trig ratios:

a/c is Opposite / Hypotenuse, which is sin(θ) b/c is Adjacent / Hypotenuse, which is cos(θ) So (a/c) 2 + (b/c) 2 = 1 can also be written:

cosX cosY = (1/2) [ cos (X - Y) + cos (X + Y) ] sinX cosY = (1/2) [ sin (X + Y) + sin (X - Y) ] cosX sinY = (1/2) [ sin (X + Y) - sin[ (X - Y) ] sinX sinY = (1/2) [ cos (X - Y) - cos (X + Y) ] Difference of Squares Formulas

2024年2月19日 · For example, the equation (sin x + 1) (sin x − 1) = 0 (sin x + 1) (sin x − 1) = 0 resembles the equation (x + 1) (x − 1) = 0, (x + 1) (x − 1) = 0, which uses the factored form of the difference of squares. Using algebra makes finding a solution straightforward and familiar.