
How do you use DeMoivre's Theorem to simplify #(5(cos20
2016年11月19日 · The answer is =125/2(1+isqrt3) DeMoivre 'theorem is (costheta+isintheta)^n= cosntheta+isinntheta Therefore, (5(cos20+isin20))^3 =5^3(cos3*20+isin3*20) =125 (cos60 ...
Prove that $\\cos20°\\cos40°\\cos60°\\cos80°=\\frac{1}{16}.$
2019年7月10日 · Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
trigonometry - Value of $\cos 20^\circ + 2 \sin^2 55^\circ
Value of $\cos 20^\circ + 2 \sin^2 55^\circ - \sqrt{2} \sin 65^\circ$. Frankly speaking, I have no idea how to start in this question.
What is #{sin10°+sin20°}/{cos10°+cos20°} - Socratic
2017年10月9日 · As #sinA+sinB=2sin((A+B)/2)cos((A-B)/2)#. and #cosA+cosB=2cos((A+B)/2)cos((A-B)/2)#. Hence #(sin10^@+sin20^@)/(cos10^@+cos20^@)#
Find the $A$ :$A=\\frac{\\tan 30^{\\circ}+\\tan 40^{\\circ}+\\tan …
2017年2月28日 · Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Cos(20°)cos(40°)cos(80°) - Socratic
2017年10月5日 · #cos20^@cos40^@cos80^@,# #=1/(2sin20^@)(2sin20^@cos20^@)cos40^@cos80^@,# …
How to prove that cos (80°)+cos(40°)-cos(20°)=0 - Socratic
2017年10月8日 · 13613 views around the world You can reuse this answer ...
How do you use the Squeeze Theorem to find lim (x^2)(cos20
2015年9月27日 · How do you use the Squeeze Theorem to find #lim (x^2)(cos20(pi*x)) # as x approaches zero?
complex numbers - Can it be proved that the closed form of …
2025年2月2日 · $\begingroup$ $\cos20^{\circ}$ is a closed form. But it can be proved that, to express it in radicals, nonreal numbers are needed. The usual proof goes via Galois Theory, and won't make much sense to you if you haven't studied that …
How do you prove that \frac { \cos 20^ { \circ } - \sin 20^ { \circ ...
2017年7月16日 · How do you prove that #\frac { \cos 20^ { \circ } - \sin 20^ { \circ } } { \cos 20^ { \circ } + \sin 20^ { \circ } } = \tan 25^ { \circ }#?