2018年3月17日 · color(brown)(cos (-30) = cos 30 = cos (pi/6) = sqrt3 / 2 = 0.866 To get exact value of cos(-30) http://www.ask-math.com/all-sin-cos-tan-rule.html cos (-30) is in IV ...

2017年1月10日 · cos(30^@)=sqrt(3)/2 Consider an equilateral triangle (with interior angles of 60^@) and sides of length 2 ...

2015年4月26日 · 30^o " and " 60^o "are angles of one of the standard triangles" sin(30^o) = 1/2 cos(30^o) = sqrt(3)/2 sin(60^o) = sqrt(3)/2 cos(60^o) = 1/2 So sin(60^o)*cos(30^o) + sin(30^o)*cos(60^o) =(sqrt3/2)(sqrt3/2) +(1/2)(1/2) = 3/4 +1/4 =1

2015年9月17日 · cos(330º) = sqrt3/2 Remember that cos(a-b) = cos(a)cos(b) + sin(a)sin(b) and that 330º = 360º - 30º, so cos(330º) = cos(360º - 30º) = cos(360º)cos(30º) + sin(360º)sin(30º) The cosine, sine, tangent and secant of 360º equal the cosine, sine, tangent and secant of 0º respectively. We know that sin0º is 0, and that cos0º = 1 so cos(330º) = 1*cos(30º) + …

2016年11月20日 · General Formula: #color(white)("XXX")cos(A+B)=cos(A) * cos(B) - sin(A) * sin(B)# Note: #75^@ = 30^@ +45^@# #30^@# and #45^@# are two of the standard angles with:

2015年10月16日 · Find exact value of tan (45 + 30). Ans: (sqrt3 + 1)/(sqrt3 - 1) tan (45 + 30) = (sin (45 + 30))/(cos (45 + 30)) Find sin (45 + 30) and cos (45 + 30) sin (45 + 30 ...

2015年5月13日 · How do I convert the polar coordinates #3(cos 210^circ +i\ sin 210^circ)# into rectangular form? What is the modulus of the complex number #z=3+3i#? What is DeMoivre's theorem?

Write the expression as the sine, cosine, or tangent of an angle. \ \cos 45^\circ \cos 120^\circ - \sin 45^\circ \sin 120^\circ; Obtain the formula of (cos c - cos d). Find sin L, cos L, tan L, sin M, cos M, and tan M. Express each ratio as a fraction and as a decimal to the nearest hundredth if necessary. l = 15, m = 36, n = 39

2015年11月21日 · Apply the trig identity: cos (a + b) = cos a.cos b - sin a.sin b #cos (75) = cos (30 + 45) = cos 30*cos 45 - sin 30*sin 45 =#

Use the half-angle identities to evaluate cos 15 degrees exactly. (Type an exact answer, using radicals as needed.) What is the exact value of the trigonometric function cos(30 degrees). Answer using radicals. Use integers or fractions for any numbers in the expression.