Oct 18, 2012 · Do you want to evaluate 2sin 18 cos 18? There are a lot of apporaches for this problem. Here I show you one approach: Let x = 18 degrees. sin 2x = sin 36 = cos 54 = cos 3x, using co-function property. Expand, 2sin x cos x = cos x cos 2x - sin x sin 2x. Cancel cos x and let u = sin x = sin 18, 2u = 1 - 2u^2 - 2u^2 = 0, sinc cos 2x = 1 - 2sin^2 x

May 1, 2018 · COS 18° -- I. In each quadrant, you find the reference by heading for the nearest X-axis. In I, it's 0. ...

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(A) 21/3[cos(23π/18) + i sin(23π/18)] (B) 21/3[cos(8π/9) + i sin(8π/9)] (C) 21/3[cos(17π/18) + i sin(17π/18) (D) 21/3[cos(10π/9) + i sin(10π/9)] (E) 21/3[cos ...

Kimberly R. asked • 05/02/20 Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one number. cos(25°) cos(65°) − sin(25°) sin(65°)

Nov 20, 2013 · cos(x-y) = cos(x)cos(y) + sin(x)sin(y) In your example, x=3pi/7 and y=2pi/21. Therefore, we can rewrite the whole expression as: cos(3pi/7 - 2pi/21) which = cos(9pi/21 - 2pi/21) = cos(7pi/21) = cos(pi/3) = 1/2. In your case, cos(pi/A)=cos(pi/3) so A=3 and B/2 = 1/2 so B=1. Does that make sense? Let me know if you have any further questions!-Ryan

sin theta = 3/5 theta = arc sin (3/5) = 36.87 deg thus, cos (thteta/2) = cos (36.87/2) = cos (18.43) = 0.9487

This calculator takes a whole number, mixed number, or fraction entered as the following examples suggest and simplifies the fraction:

Jul 18, 2020 · Since θ lies in quadrant 1, 0° < θ < 90°. So, 0° < θ/2 < 45°. Therefore, θ must also lie in the first quadrant.

Dec 2, 2020 · 1/2 · ∫ [ -7 + 14 cos(θ) ] dθ; evaluated from - π/3 to π / 3 The limits of integration are∫ from - π / 3 to π / 3, and the graph is symmetrical; therefore, one may obtain the same result by integrating from 0 to π /3 and multiplying the above integral by 2 obtaining: