NDA2017MathematicsTrigonometric Ratios & IdentitiesActual
If - cosec = 4 3 , then what is ( - ) equal to?
Options
- A-2 only
- B1 2 only
- CBoth -2 and 1 2
- DNeither 1 2 nor -2
Correct answer
B. 1 2 only
Step-by-step solution
aligned & - cosec = 4 3 1 - 1 = 4 3 & - = 4 3 & ( - )^2 ( )^2 = 16 9 & ^2 + ^2 -2 ^2 ^2 = 16 9 & 1-2 ^2 ^2 = 16 9 aligned aligned & Let =x 1-2 x x^2 = 16 9 & 16 x^2+18 x-9=0 & (8 x-3)(2 x+3)=0 & x= 3 8 , x= -3 2 & = 3 8 aligned from (i), - = 4 3 3 8 = 4 8 = 1 2