Question

shortcut for remembering trignometric values

Answer 1

Shortcut for remembering trignometric values

sine x=cosine(90°-x); cosine x=sin (90°-x).

tangent x=cotangent (90°-x);

cotangent x=tan (90°-x).

secant x=cosecant (90°-x);

cosecant x=sec (90°-x)

[where there is ‘co', there is 90°-]

1/sin=cosec; 1/cosec=sin

1/cos=sec; 1/sec=cos

1/tan=cot; 1/cot=tan.

Also, keep remembered that the sine ratio of positive angles lie in between 0 and 1; and it increases as the angle increases from 0° to 90°.

If you know all these, why should you keep remembered ALL the values of the entire table? Just remember the following:

sin 0°=0, sin 30°=1/2, sin 45°=1/√2, sin 60°=√3/2 and sin 90°=1.

If you remember these, then you know

sin 0°=cos 90°=0.

sin 30°=cos 60°=1/2

sin 45°=cos 45°=1/√2

sin 60°=cos 30°=√3/2

sin 90°=cos0°=1

And

tan0°=sin0°/cos0°=0

tan 30°=sin 30°/cos 30°=1/√3

etc.

And also,

cot 0°=1/tan 0°=infinity

sec 30°= 1 cos 30°=2/√3

cosec 45°=1/sin 45°=√2