Q. 12 B4.2( 5 Votes )
Let us write whether the following statements are true of false:
(i) The value of cos54° and sin36° are equal.
(ii) The simplified value of (sin 12° - cos78°) is 1.
Answer :
(i) The statement is true
⇒ cos54° = cos(90 - 36)°
= sin36°
[cos(90 - θ) = sinθ]
∴ the value of cos54° and sin36° has same values
(ii) The given statement is False
⇒ sin12° - cos78°
⇒ sin12° - cos(90 - 12)°
⇒ sin12° - sin12°
= 0
Rate this question :
Quiz | Task on Trigonometric Ratios46 mins
T- Ratios of Specified Angles58 mins
Quiz on Trigonometric Ratios31 mins
Trigonometric Identities33 mins
Champ Quiz | Trigonometric Identities33 mins
Testing the T- Ratios of Specified Angles57 mins
NCERT | Trigonometric Identities52 mins
Trigonometric Identities44 mins
Trick to learn all Trigonometric Formulae28 mins
Solving NCERT Questions on Trigonometric Identities56 mins
If A = B = 45°, then let us justify
sin (A+B) = sin A cos B + cos A sin B
West Bengal Board - MathematicsIf 
then let us determine the value of x.
If x2 = sin2 30° + 4 cot2 45° - sec2 60°, then let us determine the value of x.
West Bengal Board - MathematicsIf x tan 30° + y cot 60° = 0 and 2x – y tan 45° = 1, then let us write, by calculating the values of x and y.
West Bengal Board - MathematicsLet us show that:
sin66° - cos24° = 0
West Bengal Board - MathematicsLet us show that:
cosec248° - tan242° = 1
West Bengal Board - Mathematicslet us find the value of
If sec 5A = cosec (A + 36°) and 5A is a positive acute angle, let us find the value of A.
West Bengal Board - Mathematicslet us find the value of (tan 1° × tan2° × tan 3°………..tan89°)
West Bengal Board - MathematicsLet us show that,
