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Showing 2 questions for Class 10. Tap a card to reveal the answer.

MathematicsIntroduction to Trigonometrymedium

If sin(theta) = 3/5, find cos(theta) and tan(theta), where theta is acute.

Reveal answer ↓

What it is

The identity sin^2 + cos^2 = 1 lets you find one trig ratio from another for the same angle.

Answer

Using the identity sin^2(theta) + cos^2(theta) = 1, cos^2(theta) = 1 - (3/5)^2 = 1 - 9/25 = 16/25, so cos(theta) = 4/5 (positive since theta is acute). Then tan(theta) = sin/cos = (3/5) / (4/5) = 3/4.

sin^2(theta) + cos^2(theta) = 1 ; tan = sin/cos

  • sin^2 + cos^2 = 1
  • cos(theta) = 4/5
  • tan(theta) = sin/cos = 3/4

Why learn this

Trig ratios drive navigation, physics waves, construction and computer graphics.

💡 Memory trick

Think of the 3-4-5 triangle: sin 3/5 -> cos 4/5 -> tan 3/4.

MathematicsIntroduction to Trigonometrymedium

Evaluate 2 tan^2(45 degrees) + cos^2(30 degrees) - sin^2(60 degrees).

Reveal answer ↓

What it is

The standard angles 0, 30, 45, 60 and 90 degrees have fixed trig values worth memorising.

Answer

Use standard values: tan(45 deg) = 1, cos(30 deg) = sqrt(3)/2, sin(60 deg) = sqrt(3)/2. So the expression = 2(1)^2 + (sqrt(3)/2)^2 - (sqrt(3)/2)^2 = 2 + 3/4 - 3/4 = 2.

tan45 = 1 ; cos30 = sqrt(3)/2 ; sin60 = sqrt(3)/2

  • tan45 = 1, cos30 = sin60 = sqrt(3)/2
  • 2(1) + 3/4 - 3/4
  • = 2

Why learn this

They appear in nearly every physics and maths problem - knowing them saves huge time.

💡 Memory trick

For sin, use sqrt(0..4)/2 across 0,30,45,60,90; cos is the same list reversed.