Question

ii) yz 13-20 COC2-6)
5 5​

Answer 1

sin(90+x)=+cos x (since sin x is positive in second quadrant.)

cos(90+x)= -(sin x) (since cos x is negative in second quadrant.)

and

As you can see from the graph.

• In first quadrant all trigonometric value will remain positive.
• In second quadrant only Sin & Cosine will be positive while other trigonometric values will be negative.
• In third quadrant only Tan & Cot will remain positive kepping other trigonometric values negative.
• In forth quadrant only Cos &. Sec will be positive kepping all other quantities negative.

Now According to question

Sin 120 = Sin(180–60)

= Sin 60

= √3/2

or

sin(90+x)=cosx

sin120=sin(90+30)=cos30=(√3)/2=0.867