
Trigonometry Trigonometry Math Forum 
 LinkBack  Thread Tools  Display Modes 
December 11th, 2016, 08:32 PM  #1 
Newbie Joined: Dec 2016 From: USA Posts: 11 Thanks: 0  Hard problemFind the exact value
(Sin7.5°cos7.5°)(sin7.5°+cos7.5°)(sin7.5°cos7.5°)(tan7.5°)(cot7.5°)=

December 11th, 2016, 09:11 PM  #2  
Math Team Joined: Jul 2011 From: Texas Posts: 2,426 Thanks: 1195  Quote:
$(\sin{7.5}\cos{7.5})(\sin^2{7.5}\cos^2{7.5})(1)$ Note $\cos^2{t}\sin^2{t}=\cos(2t)$ and $2\sin{t}\cos{t}=\sin(2t)$ ... $\left(\dfrac{1}{2} \cdot 2\sin{7.5}\cos{7.5}\right)(\cos{15})$ $\dfrac{1}{2}\sin{15}\cos{15}$ $\dfrac{1}{4} \cdot 2\sin{15}\cos{15}$ $\dfrac{1}{4} \sin{30} = \dfrac{1}{8}$  

Tags 
exact, hard, problemfind 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Find the Exact Value  Shamieh  Algebra  4  April 30th, 2013 12:08 PM 
How to find the exact answer on this derivative?  davedave  Calculus  16  November 9th, 2012 12:23 AM 
Finding exact value problem.  hirano  Algebra  5  September 12th, 2010 04:56 AM 
find the exact value of the following expression help  Tcanuth  Algebra  6  September 25th, 2008 06:02 AM 
Find the Exact Value  Shamieh  Calculus  4  January 1st, 1970 12:00 AM 