The key is to write 195 degrees as the sum or difference of two numbers whose sine and cosine are known. cos195 = cos(45 + 150). NOTE: 45 + 150 = 195. We need to use the sum formula for cosine. We use this: cos(A + B) = cosAcosB - sinAsinB Let A = 45 and B = 150 cos(45 + 150) = cos45cos150 - sin45sin150

2015年8月30日 · color(red)(cos195 = -sqrt(2 +sqrt3)/2) > The cosine half-angle formula is cos(x/2) = ±sqrt((1 + cos x) / 2) The sign is positive if x/2 is in the first or fourth quadrant and negative if x/2 is in the second or third quadrant. ∴ cos195 = cos(180+15) = -cos15 15° is in the first quadrant, so we use the positive sign. cos15 =cos(30/2) = sqrt((1+cos30)/2) cos15 …

2015年4月25日 · Find two special angles that add up to #195^@# #(30+ 165)^@#. -- no #165^@# is not a special angle #(45+150)^@#. Yes that will work. (So would #(60+135)^@#) #cos195^@ = cos(45^@ + 150^@)# Now use the formula and …

2015年6月6日 · Use trig identity #2cos^2a = 1 + cos 2a#. #cos 390 = cos (30 +360) = cos 30 = sqrt3/2# #2cos^2 195 = 1 + cos 390 = 1 + 0.866 = 1.866#

2015年8月27日 · color(red)(sin(195) = (1-sqrt3)/(2sqrt2)) > I will use 195 = 150 + 45 ∴ sin(195)= sin(150+45) The sine sum identity is: sin(A+B) = sinAcosB+cosAsinB ∴ sin(195) = sin(150)cos(45) + cos(150)sin(45) We can use the unit circle to work out the values.

You can write 195° as any one of these: 150°+45°, 135°+60°, 225°-30°, 240°-45°, 315°-120°, 330°-135° If you choose to use the first one, 150°+45°, you then use

2015年10月24日 · Find the value of sec (1275) Ans: - (2sqrt2)/(1 + sqrt3) sec (1275) = 1/(cos 1275). First, find cos (1275). cos 1275 = cos (195 + 1080) = cos (195 + 3(360)) = cos ...

Question 855445: Find the exact values of the sine, cosine, and tangent of the angle. 195° = 240° − 45° sin(195°)

cos 195° Algebra -> Trigonometry-basics -> SOLUTION: Use an Addition or Subtraction Formula to find the exact value of the expression. Algebra: Trigonometry Section

You can put this solution on YOUR website! find the exact value of cos 195 degrees + cos 105 degrees ** Sum to product formula: