Grade 11Trigonometry
Prove that cos3a+2cos5a+cos7a/cos a +2cos3a+ cos5a equals to cos2a-sin2atan3a
Prove that cos3a+2cos5a+cos7a/cos a +2cos3a+ cos5a equals to cos2a-sin2atan3a
1 Answer
Arun
Dear student
cos3A+2cos5A+cos7A)/(cosA+2cos3A+cos5A)
= 2cos 5A [cos 2A + 1] / 2cos 3A [cos 2A + 1]
= cos 5A / cos 3A
= [cos 3A cos 2A -- sin 3A sin 2A] /cos 3A
= cos 2A -- sin 2A tan 3A
= 2cos 5A [cos 2A + 1] / 2cos 3A [cos 2A + 1]
= cos 5A / cos 3A
= [cos 3A cos 2A -- sin 3A sin 2A] /cos 3A
= cos 2A -- sin 2A tan 3A
Regards
Arun
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