help@askiitians.com

1800-150-456-789

Trigonometry> prove that (sin 2 39-sin 2 21)(sin 2 57-s...

question mark

prove that (sin239-sin221)(sin257-sin23)=3/16:-

suvrasanta chakraborty , 10 Years ago

Grade

1 Answers

Sumit Majumdar

Last Activity: 10 Years ago

Solution:

We have:

$sin(239)-sin(221)=2cos(230)sin(9) and sin(257)-sin(23)=2cos(140)sin(117)$

So,

we get:

$(sin(239)-sin(221))*(sin(257)-sin(23)) =4cos(230)sin(9)cos(140)sin(117) =-\left (2sin(140)cos\left (140 \right ) \right )\left (2cos\left (27 \right )cos\left (81 \right ) \right ) =-sin(280)\left (cos(108)+cos(54) \right ) =sin(80)sin(18)-sin(80)sin(36) =sin(80)(sin(18)-2sin(18)cos(18)) =sin(18)cos(10)(1-2cos(18))$ Regards

Sumit

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

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 Years ago

Find the general solution of equation tan3∂=cot2∂
For all angles between -720 and +720

trigonometry

0 Answer Available

Last Activity: 3 Years ago

To prove : Cosec(45 degree - A)Cosec(45 degree + A) = 2SecA

trigonometry

0 Answer Available

Last Activity: 3 Years ago

cos^2 13ºcos^2 47º+cos^2 73º =? …..................

trigonometry

0 Answer Available

Last Activity: 3 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)

trigonometry

0 Answer Available

Last Activity: 3 Years ago

View all Questions