Find the value of cos 75
kashmir , 10 Years ago
Grade
Trigonometry> Find the value of cos 75
2 AnswersRinkoo Gupta
Last Activity: 10 Years ago
cos75=cos(90-15)=sin15
sin^@=(1-cos(2@))/2
sin^15=(1-cos30)/2
=(1-(sqrt(3))/2)/2
=(2-sqrt3)/4
sin15=sqrt(2-sqrt3)/2
hence cos75=sqrt(2-sqrt3)/2 Ans.
Thanks & Regards
Rinkoo Gupta
AskIITians Faculty
Manas Satish Bedmutha
Last Activity: 10 Years ago
Simply using, cos 2A = 2 cos^2 A - 1 For A = 75, cos 150 = 2cos^2 75 - 1 = - cos 30 So, cos^2 75 = 1 - cos 30 = (2-sqrt3)/2x2 Hence, cos 75 = sqrt( (2-sqrt3) ) / 2
Provide a better Answer & Earn Cool Goodies
Enter text here...
LIVE ONLINE CLASSES
Prepraring for the competition made easy just by live online class.
Full Live Access
Study Material
Live Doubts Solving
Daily Class Assignments
Ask a Doubt
Get your questions answered by the expert for free
Enter text here...
Other Related Questions on Trigonometry
In ABC, if cot A+cot B+cot C = cosecA cosecB cosecC, then prove that ABC is right angle triangle.
Trigonometry
1 Answer Available
Last Activity: 2 Year ago(s)
Find the general solution of equation tan3∂=cot2∂For all angles between -720 and +720
Trigonometry
0 Answer Available
Last Activity: 2 Year ago(s)
To prove : Cosec(45 degree - A)Cosec(45 degree + A) = 2SecA
Trigonometry
0 Answer Available
Last Activity: 2 Year ago(s)
cos^2 13ºcos^2 47º+cos^2 73º =? …..................
Trigonometry
0 Answer Available
Last Activity: 2 Year ago(s)
Derive a formula for the area of the triangle, given b, A, B, and C. That is, derive the formula: (b^2sinAsinC)/(2sinB)
Trigonometry
0 Answer Available
Last Activity: 2 Year ago(s)