Home
Class 11
MATHS
Cos (-(9pi)/(4))=...

`Cos (-(9pi)/(4))=`

A

0

B

-1

C

`-(1)/(sqrt(2))`

D

`(1)/(sqrt(2))`

Text Solution

Verified by Experts

Promotional Banner

Similar Questions

Explore conceptually related problems

Which of the following quantities are rational? (a) sin((11pi)/(12))sin((5pi)/(12)) (b) cos e c((9pi)/(10))sec((4pi)/5) (c) sin^4(pi/8)+cos^4(pi/8) (d) (1+cos((2pi)/9))(1+cos((4pi)/9))(1+cos((8pi)/9))

Prove that: i) sin(5pi)/(18) - cos(4pi)/(9) = sqrt(3)sinpi/9 ii) cos(3pi)/4+A-cos((3pi)/(4)-A)=-sqrt(2)sinA

cos((3pi)/(4)+x)-cos((3pi)/(4)-x) = -sqrt(2)sinx

Prove that: cos((3pi)/(4)+A)-cos((3pi)/(4)-A)=-sqrt(2)sinA

sin^(-1)(sin((9pi)/4))

cos((pi)/(4)-x)cos((pi)/(4)-y)-sin((pi)/(4)-x)sin((pi)/(4)-y)=sin(x+y)

Show that 16cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((16pi)/(15))=1

Prove that cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((14pi)/(15))=1/(16)

Prove that cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((16pi)/(15))=1/(16)

If A+B+C=pi , prove that : (sin ((B+C)/(2)) + sin ((C+A)/(2)) + sin( (A+B)/(2) )) equals (4cos ((pi-A)/(4)) cos( (pi-B)/(4)) cos((pi-C)/(4))) .