Trigonometry
Find the value of cos 75
2 Answers
Rinkoo Gupta
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
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
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.
In ABC, if cot A+cot B+cot C = cosecA cosecB cosecC, then prove that ABC is right angle triangle.
trigonometry
Last Activity: 3 Years ago
- Find the general solution of equation tan3∂=cot2∂
For all angles between -720 and +720
- Find the general solution of equation tan3∂=cot2∂
For all angles between -720 and +720
trigonometry
Last Activity: 4 Years ago
Derive a formula for the area of the triangle, given b, A, B, and C. That is, derive the formula: (b^2sinAsinC)/(2sinB)
Derive a formula for the area of the triangle, given b, A, B, and C. That is, derive the formula: (b^2sinAsinC)/(2sinB)
trigonometry
Last Activity: 4 Years ago
WHAT IS THE LIMIT WHEN X TOWARDS TO 0 OF sin6x/5x ? lim𝑥→0 𝑠𝑖𝑛6𝑥/5𝑥
WHAT IS THE LIMIT WHEN X TOWARDS TO 0 OF sin6x/5x ? lim𝑥→0 𝑠𝑖𝑛6𝑥/5𝑥
trigonometry
Last Activity: 4 Years ago