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For example, the sine of angle θ is defined as being the length of the opposite side divided by the length of the hypotenuse. The six trigonometric functions are defined for every real number , except, for some of them, for angles that differ from 0 by a multiple of the right angle (90°).
In trigonometry, the law of sines, sine law, sine formula, or sine rule is an equation relating the lengths of the sides of any triangle to the sines of its angles. According to the law, = = =, where a, b, and c are the lengths of the sides of a triangle, and α, β, and γ are the opposite angles (see figure 2), while R is the radius of the triangle's circumcircle.
Fig. 1a – Sine and cosine of an angle θ defined using the unit circle Indication of the sign and amount of key angles according to rotation direction Trigonometric ratios can also be represented using the unit circle , which is the circle of radius 1 centered at the origin in the plane. [ 37 ]
The sine rule gives C and then we have Case 7. There are either one or two solutions. Case 4: two angles and an included side given (ASA). The four-part cotangent formulae for sets (cBaC) and (BaCb) give c and b, then A follows from the sine rule. Case 5: two angles and an opposite side given (AAS). The sine rule gives b and then we have Case 7 ...
The half-angle formula for sine can be obtained by replacing with / and taking the square-root of both sides: (/) = () /. Note that this figure also illustrates, in the vertical line segment E B ¯ {\displaystyle {\overline {EB}}} , that sin 2 θ = 2 sin θ cos θ {\displaystyle \sin 2\theta =2\sin \theta \cos \theta } .
A related question is whether it can be expressed using cube roots. The following two approaches can be used, but both result in an expression that involves the cube root of a complex number . Using the triple-angle identity, we can identify sin ( 1 ∘ ) {\displaystyle \sin(1^{\circ })} as a root of a cubic polynomial: sin ( 3 ∘ ...
Section B contains 4 questions where students are given the choice to answer 3 out of 4 of them. Section C contains 4 questions where students are only required to answer 2 out of 4 of the given questions. All Section C questions are based on the same chapters every year and are thus predictable.
The reason is that the value of sine for the angle of the triangle does not uniquely determine this angle. For example, if sin β = 0.5 , the angle β can equal either 30° or 150°. Using the law of cosines avoids this problem: within the interval from 0° to 180° the cosine value unambiguously determines its angle.