✔ Sine of thirty degrees is the ratio of opposite to hypotenuse, which equals one-half.
Q2. Which angle has a cosine value of zero?
✔ Cosine decreases as the angle increases, reaching zero at ninety degrees.
Q3. What is tan(45 degrees) equal to?
✔ At forty-five degrees, the opposite and adjacent sides are equal, so their ratio is one.
Show transcript
[Slide 1] Why Special Angles Matter
Trigonometry relies on ratios in right-angled triangles. Special angles give us exact values without calculators. This foundation helps solve complex geometry problems quickly.
[Slide 2] The Five Standard Angles
You must know values for five specific angles. These are zero, thirty, forty-five, sixty, and ninety degrees. CBSE questions frequently test these exact values.
[Slide 3] Calculating Sine of Thirty Degrees
Let us find the sine of thirty degrees. In a standard triangle, the opposite side is one and hypotenuse is two. Dividing one by two gives the exact value.
[Slide 4] Avoid Swapping Sine and Cosine
A common error is swapping sine and cosine for thirty degrees. Remember sine values increase as angles get larger. Always double-check your memorized table before writing.
[Slide 5] Quick Revision for Boards
Review this table every morning before school. Solving past papers ensures you recognize these values instantly. Consistent practice guarantees full marks in this section.