How do you find the value of tan-135°?
Calculate the value of trigonometric ratio at given angle:
Let x be the value of tan-135°.
∴x=tan-135°
=-tan135° [∵tan-a=-tana]
=-tan1×90°+45
=-sin90°+45°cos90°+45° [∵tanθ=sinθcosθ]
=-cos45°-sin45° [∵sin90°+a°=cosa°;cos90°+a°=-sina°]
=1212 [∵sin45°=12;cos45°=12]
=1
Hence, the value of tan(-135°) is 1.
Can you do these in your head?
(i) (135 − 73) − 27
(ii)
(iii) (298 − 4.5) − 3.5